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Interim Wetland Functional Assessment Model for the Nebraska Sand Hills

PRAIRIE POTHOLE
WETLAND TEAM
NORTHERN PLAINS REGION, NRCS
P. O. BOX 1489
JAMESTOWN, NORTH DAKOTA 58402-1489

http://www.@ndwet@nd.nrcs.usda.gov

February 1, 1999

INTERIM WETLAND FUNCTIONAL ASSESSMENT MODEL FOR THE NEBRASKA SAND HILLS

Version 1.0

TABLE OF CONTENTS

I. Functional profile

II. Model Explanation

A. Hydrology Function

1.0 Maintain Characteristic Hydrology

B. Biogeochemical Functions

2.0 Removal, Conversion and Release of Elements and Compounds

3.0 Retention of Particulates

C. Biotic and Habitat Functions

4.0 Maintain Characteristic Plant Community

5.0 Maintenance of Habitat Structure Within Wetland

6.0 Maintenance of Habitat Interspersion and Connectivity Among Wetlands

III. Field Guide for Determination and Measurements of Indicators

A. Introduction

B. Guidelines for Assessing Wetland Functions

C. Tools for Functional Assessments

D. Preferred Order of Assessing Variables

E. Detailed Instructions for Determination and Measurement of Indicators

VI. Appendix

A. Comments on Variables

B. Field Forms for Data Collection for Functional Assessment

C. Explanation of Files Stored on Computer Disk

D. Literature Cited

I. FUNCTIONAL  PROFILE

Subclass Name: Depressional, Endo-saturated, Highly Permeable Substrate, Temporary and Seasonal Wetlands.

Reference Domain: MLRA 65 Nebraska Sandhills in Nebraska and South Dakota.

Existing Classification:

National Wetlands Inventory—PEMA, PEMB, PEMC

Stewart & Kantrud -- Class II and Class III

Circular 39 -- Type 1 and 3

Climate:

Cool sub-humid, cold winters and hot summers, broad seasonal fluctuations in precipitation and temperature.

Geomorphic Setting: Closed depressions The amount of topographic relief in this interim model is being held to dominant slopes of less than 9% within the catchment area of the wetland. This information can be obtained from the soil survey and checked on site. As the relief increases the amount of sediment from erosion also increases even on well managed native prairie in the sandhills.

Geologic Materials: Sandy alluvial deposits modified by wind. Drainage pattern not well defined, high water table, hummocky sands with low to moderate relief (2-20 feet).

Soil Types:

Wetland Soils—Tryon, Loup and Hoffland soils

Associated Upland Soils—Valentine, Valent, Els, Elsmere and Ipage soils.

Hydrology

Water sources: Principally ground water with precipitation.

Water losses: Evapotranspiration. Hydro-period fluctuations with upward, downward and lateral movement of water.

Hydrodynamics: Mainly lateral with some vertical fluctuations within the wetland

Hydrologic Functions: Dominated by moderating groundwater flow.

What are the most common alterations that may impact hydrology? Irrigation, land leveling, tiling, filling, tillage and ditches.

Vegetative communities(NWI or other classification schemes) Range Sites: Subirrigated, Wet Meadow, Wet Subirrigated and Wetland

Fully functional ecosystem characterized by: Tall and mixed grass, warm season herbaceous vegetation on uplands with native herbaceous vegetation in wetlands.

Somewhat impaired ecosystem characterized by: Cool season introduced vegetation/ overgrazed eroding soils.

Critically impaired ecosystem characterized by intensive cultivation: Irrigated low residue crop production - Corn, corn silage and soybeans.

Vegetative Red Flags (T&E): Orchids(western prairie fringe) on temporary wetland fringe.

Noxious plants/ invaders: Leafy Spurge, Canada Thistle

Existing vegetative classification other(not NWI): Low Prairie zone, Wet Meadow zone, and Shallow Marsh zone.

Habitat: What kind of "critters" rely on this subclass for part or all of their life cycles:

shore birds, waterfowl, amphibians, reptiles and some mammals.

Any Threatened and Endangered species—

Live here: American Burying Beetle - South Dakota

Pass through: Bald eagle, peregrine falcon, whooping crane

Rely on: none

Does this subclass exist in a complex

with similar wetlands: YES

with other types of wetlands: YES Semi-permanent.

Is ecosystem fragmentation an issue: YES

Biogeochemical Functions: Removal of elements and compounds, nutrient cycling, particulate retention.

What common impacts might impair biogeochemical functions:

1. Lowering of groundwater level by irrigation

2. Tile drainage

3. Filling of low areas

4. Application of fertilizer and chemicals

5. Removal of native vegetation from wetland and upland

6. Surface ditches

Version. 1.0

II. Model Explanation

INTERIM FUNCTIONAL ASSESSMENT MODEL FOR TEMPORARY AND SEASONAL WETLANDS ON THE SANDHILLS IN NEBRASKA AND SOUTH DAKOTA.

Notes: This Interim Sandhill HGM Model is patterned after the Lake Dakota Sand Plains Interim Model and the Northern Prairie Pothole Model by Lee, L.C. et al (1997). Many of the definitions, logic, rationale, functions, and variables have been taken from the model, however, not all of the functions and variables have been included in this interim model.

The Prairie Pothole Resource Technical Team wishes to thank Gerald Jasmer, NRCS State Biologist, Lincoln, Nebraska for his help with consultation, review and assistance with sections of this model.

1.0 MAINTAIN CHARACTERISTIC HYDROLOGY

DEFINITION: The capacity of the wetland to regulate the outflow and/or the inflow and the ability of the wetland to provide storage of water.

Effects On-Site: Contributes to the maintenance of characteristic soils, vegetation, invertebrate and vertebrate communities, and provides for water storage.

Effects Off-Site: Modifies off-site hydrology of wetland and riverine systems within the groundwater flow net.

Discussion of Function:

A combination of the geological material and the regional water balance in the sand hills leads to moderation of ground water flow within the depressions. The principal water sources for the sand hill depressional wetlands are from groundwater and precipitation, and the principal water loss is through evapotranspiration. These hydro-dynamics produce an inter- and intra-annual cycle of ground water exposure and water storage above and below the edge of the temporary wetlands. This cycle supports the diverse plant and animal habitats as well as biogeochemical processes. These sand hill depressional wetlands sustain the hydrological cycle. The hydrological dynamics of the Prairie Pothole Region are addressed by Stewart and Kantrud (1972), Winter (1989) and Kantrud et al. (1989).

1.0 INDEX OF FUNCTION: Maintain Characteristic Hydrology

={Vhydalt * [(Vsource + Vupuse + Vsed)/3 + (((Vsorpt +Vpore)/2) + Vwetuse)/2]/2}1/2

 Discussion of Variables:

The variables associated with the performance of this function focus on land use and on the physical integrity of soil conditions. Human activities at nearby lower elevations and above or within the wetland affect the rate of ground water movement and quantity of surface and subsurface water entering and leaving the wetland. Vupuse, Vwetuse, and Vsource are used to describe potential alterations of water flow to the wetlands. Land use activities also affect erosion and sediment import into the wetlands by water and wind. An increased sediment load will decrease the wetland’s capacity to expose water and trap water to be routed to the groundwater. The degree of sedimentation is captured by the Vsed variable. Undisturbed soil conditions within the wetland are closely related to ground water movement and water storage, through the ability of the soil to transmit and hold water interstitially. This soil condition is described in the Vsorpt and Vpore variable. Finally, the elevation of surface or subsurface outlets inside and outside of the wetland temporary zone boundary and fill placed in the wetland impacts surface water elevations and, therefore, the ability of the depression to capture and expose groundwater. The Vhydalt variable reflects this aspect of the function.  

1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: The depth of fill or changes in the depth of the subsurface or surface drain and distance form the wetland impacts wetland groundwater surface elevation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

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1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vsource: Source Area of Flow to Wetland

DEFINITION: The area surrounding a wetland that defines the catchment and groundwater flow area to the wetland.

LOGIC: Altering surface flow patterns within the watershed and groundwater flow area will impact ground water elevation within the basin.

Alteration of upland watershed source area by surface alterations (e.g., ditches, roads, terraces, irrigation) does not impact wetland, and NO subsurface alterations within a 1/4 mile (e.g., tile drains, ditches, irrigation wells).

Surface alterations of upland watershed source area impacts overland flow into wetland (e.g., ditches, roads, terraces, irrigation, etc.), however , no subsurface alterations(e.g., tile drains, irrigation wells).

Indicator:

Subsurface Impacts are between 1320 and 900 feet AND 3 feet or greater in elevation below the wetland bottom. Surface impacts reduce effective catchment by 25 percent OR an increase of up to 125 to the catchment.

Upland watershed source area is changed to alter the dominant surface (26 to 50 percent and subsurface flow path (899 to 500 feet away AND 3 feet or greater in elevation below the bottom of the wetland) of water to the wetland(e.g., draining or irrigation return or draw-down).

-AND-

Alteration does not change the NWI classification.

 

Upland watershed source area (25 percent or less is intact) is changed to alter the dominant surface flow path of water to the wetland (e.g., draining or irrigation return or draw-down).

-AND-

Alteration does change the NWI classification.

Upland watershed source area extremely altered such that almost all water flow to wetland eliminated (e.g., urbanization).

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1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic: Upland land use impacts the evapo-transpiration process that influences the quantity and quality of groundwater flow to the wetland. Upland land use also controls sediment delivery to the wetland which affects water storage capacity.

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

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1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC: The amount of sediment in the basin impacts the capacity of the wetland to moderate groundwater flow and store water.

 

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

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1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vsorpt: Soil Sorptive Properties for loamy sand and loamy fine sand textures

DEFINITION: The ability of the upper part of the soil to retain and move elements and compounds.

LOGIC: In sandy soils, organic matter content helps moderate the flow of water in the A horizon.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NOTE: See appendix for soils with SL and FSL textures.

 

1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vpore: Soil Porosity

DEFINITION: The ability of the soil to allow movement of liquids, gases, etc. into, and through, the upper part of the soil as indicated by the physical integrity of the upper part of the soil. This includes the number and continuity of pores, the type, grade, and size of soil structure, and the soils rupture resistance.

 

LOGIC: Saturated hydraulic conductivity is related to pores in the soil. Reduced hydraulic conductivity impacts moderation of groundwater flow.

 

Note: Direct Measurement of Vpore is Soil infiltration / permeability measurements in the upper 12" of the soil. No standards set at this time.

 

Secondary Measure - The upper (12") soil horizons structure, i.e. the A1 weak or moderate granular structure. The A2 has weak subangular blocky parting to weak or moderate granular structure.

Many very fine and fine, continuous pores.

Rupture resistance is very friable.(very slight force)

Indicator - No evidence of an Ap within hydric soil boundary.

Secondary Measure - Weak subangular blocky and/or weak granular structure -and/or- Medium and coarse plate-like structure below the plow layer.

Common very fine and fine, continuous and discontinuous pores.

Rupture resistance is friable.(slight force)

Indicator - Ap horizon is present. Wetland is partially tilled or restored (cropland) < 20 years

Secondary Measure - Massive or coarse subangular blocky -and/or- Strong coarse plate-like structure (coarse, cloddy)below Ap horizon.

-AND-

Rupture resistance is friable to firm.(slight to moderate force) Few very fine and fine discontinuous pores.

Indicator - Plow pan evidenced by roots growing horizontally along pan. Ap horizon present. Wetland is tilled throughout most years.

The substrate is a non-porous medium, i.e., asphalt, concrete, etc.

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1.0 maintain characteristic hydrology
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: Land use in the wetland affects soil pore space and vegetation-/evapo-transpiration relationships that influence characteristic hydrology

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

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 2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS

DEFINITION: Short- and long-term cycling and removal of elements and compounds on site through the abiotic and biotic processes that convert elements from one form to another and cycle nutrients.

Effects On-Site: Net effects of removal, conversion and release are balanced between gains through import processes and losses through hydrologic export, release to the atmosphere, long-term retention in persistent biomass and sediments, and cycling.

Effects Off-Site: Removal of elements and compounds and nutrient cycling on site decreases probability of export to aquatic ecosystems down-gradient and consequent nutrient loading.

Discussion of Function

The use of the term cycling refers to the annual turnover or release of nutrients and removal refers to the relatively long term accumulation or loss through conversion or removal of elements and compounds from incoming water sources. Elements include macronutrients essential to plant growth(e.g., nitrogen, phosphorous, potassium etc.) and other elements such as heavy metals (e.g., zinc, chromium, etc.) that can be toxic at high concentrations. Compounds include herbicides, pesticides, and other imported materials. Mechanisms of cycling, removal, conversion and release include sorption, sedimentation, denitrification, burial, decomposition to inactive forms, decay, uptake and incorporation into short and long-lived annual and perennial herbaceous biomass, and similar processes(Brinson et al. (1985).

 

2.0 INDEX OF FUNCTION: Removal, Conversion and Release of Elements and Compounds

=[Vsorpt + Vpore + Vpcover + Vdetritus +(Vsource + Vhydalt)/2 + (Vwetuse + Vsed + Vbuffer + Vupuse)/4]/6

Discussion of Variables

The variables within this function reflect land use, abiotic, and biotic components. Land use activities impact the magnitude of elements and compounds entering the system and the natural cycling and removal processes of the elements and compounds. Land use is reflected by upland land use, wetland land use, and sediment delivery variables. (Vupuse, Vwetuse, and Vsed respectively). In addition, the condition, continuity, and width of a buffer around the wetland influences the amount of sediment and soluble elements and compounds delivered to the wetland. The impact of a buffer is reflected by the Vbuffer variable.

Biotic components of the wetland ecosystem cycle and retain elements and compounds through biomass accumulation and litter production. Elements and compounds are recycled annually through decay and decomposition, however Neely and Baker (1989) report decay rates for some emergent plants in the Prairie Pothole region to be greater than one year indicating removal. These decomposition rates facilitate both cycling on an annual basis and removal on a longer than one year basis within the wetland. Biotic components consist of the plant and detritus variables (Vpcover and Vdetritus,) respectively.

The abiotic components assist reduction and oxidation processes that biogeochemically cycle and remove elements and compounds. Abiotic components are represented by the soil integrity (Vsorpt and Vpore), and amount/presence of water represented by the (Vhydalt and Vsource) variables.

 

2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vsorpt: Soil Sorptive Properties for loamy sand and loamy fine sand textures

DEFINITION: The ability of the upper part of the soil to retain and move elements and compounds.

LOGIC: In sandy soils organic matter content affects the sorptive capacity of soils to hold elements and compounds for release, removal, and conversion.

 

 

 

 

 

 

 

 

 

 

 

 

 

NOTE: See appendix for soils with SL and FSL textures.

Organic Matter is >2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a neutral hue with a value of 2 or 3.

-OR-

The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of <=3 and chroma of <2 and lacks a darker-colored A horizon immediately or contiguously below 6 inches.

-OR-

Site has no evidence of drainage or excessive vegetation removal

 

Organic Matter is 0.5 to =<2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >3 to <=4 and chroma of <=2.

-OR-

Site has been partially drained and/or there is evidence of intermittent or past cropping or excessive vegetation removal.

 

Organic Matter is <0.5% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >4 AND/OR chroma of >2.

-OR-

Site has been "effectively" drained and frequently cropped.

Wetland soil has been replaced by upland fill, asphalt, concrete, etc.

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2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vpore: Soil Porosity

DEFINITION: The ability of the soil to allow movement of liquids, gases, etc. into, and through, the upper part of the soil as indicated by the physical integrity of the upper part of the soil. This includes the number and continuity of pores, the type, grade, and size of soil structure, and the soils rupture resistance.

 

LOGIC: Soil pores provide surface area for soil water contact and, therefore, increased surface area for microbial activity.

 

Note: Direct Measurement of Vpore is Soil infiltration / permeability measurements in the upper 12" of the soil. No standards set at this time.

 

Secondary Measure - The upper (12") soil horizons structure, i.e. the A1 weak or moderate granular structure. The A2 has weak subangular blocky parting to weak or moderate granular structure.

Many very fine and fine, continuous pores.

Rupture resistance is very friable.(very slight force)

Indicator - No evidence of an Ap within hydric soil boundary.

Secondary Measure - Weak subangular blocky and/or weak granular structure -and/or- Medium and coarse plate-like structure below the plow layer.

Common very fine and fine, continuous and discontinuous pores.

Rupture resistance is friable.(slight force)

Indicator - Ap horizon is present. Wetland is partially tilled or restored (cropland) < 20 years

Secondary Measure - Massive or coarse subangular blocky -and/or- Strong coarse plate-like structure (coarse, cloddy)below Ap horizon.

-AND-

Rupture resistance is friable to firm.(slight to moderate force) Few very fine and fine discontinuous pores.

Indicator - Plow pan evidenced by roots growing horizontally along pan. Ap horizon present. Wetland is tilled throughout most years.

The substrate is a non-porous medium, i.e., asphalt, concrete, etc.

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2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS

Model Variable Measurement or Condition Index
Vpcover: Plant Cover Vegetation covers the ground and is dominated by perennial hydrophytes on >95% of the wetland area, vegetation is not suppressed by tillage, spraying, severe livestock overuse, or other problems. 1.0

 

 

Definition: The typical inter- and intra-seasonal abundance of woody and herbaceous plants in all vegetation zones within the wetland. Vegetation covers the ground and is dominated by perennial hydrophytes on 66% to 95% of the wetland area.

- OR -

Wetland perennial vegetation is slightly thinned by livestock overuse.

0.75

 

 

 

 

Logic: Living plant biomass cycles nutrients through (1) soil and water nutrient uptake, (2) biomass accumulation, and (3) litter production. Vegetation covers the ground and is dominated by perennial hydrophytes on 41% to 65% of the wetland area.

- OR -

Perennial hydrophyte vegetation is severely thinned by livestock overuse.

- OR -

Wetland is sometimes tilled or sprayed, but long-term average annual growth of weeds and/or crop achieves 100% canopy.

 

0.5

  Vegetation covers the ground and is dominated by perennial hydrophytes on 20% to 40% of the wetland area.

- OR -

Wetland is frequently tilled or sprayed but average annual growth of weeds and/or crop achieves 75% to 99% canopy cover.

 

0.25

  Vegetation covers the ground and is dominated by perennial hydrophytes on >1% to 19% of wetland area.

- OR -

Wetland is intensively cultivated or sprayed most years, most weed growth is suppressed and total crop growth average is only fair.

 

0.1

  Vegetation is virtually absent due to extreme effects such as continuous feedlot use.

 

 

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2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vdetritus: Detritus

DEFINITION: The typical inter and intra-seasonal amount of dead plant material in several stages of decomposition.

LOGIC: Provides an energy source and increased surface area for microbial processing of nutrients.

Temporary Zone - .75 to 2.5 inches

Seasonal Zone --- 2.25 to 6.25 inches

Temporary Zone - .5 to .75 inch -OR- >2.5inches

Seasonal Zone --- 1.5 to 2.25 inches -OR- >6.25 inches

Temporary Zone - .25 to .5 inches

Seasonal Zone --- .75 to 1.5 inches

Temporary Zone - .1 to .25 inches

Seasonal Zone --- ..25 to .75 inches

Temporary Zone - >0 to .1 inches(trace)

Seasonal Zone --- >0 to .25 inches

Litter absent

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2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vsource: Source Area of Flow to Wetland

DEFINITION: The area surrounding a wetland that defines the catchment and groundwater flow area to the wetland.

LOGIC: Altering drainage patterns within watershed and ground water flow area will impact ground water elevation within the basin that impacts characteristic removal, conversion, and release of elements and compounds.

Alteration of upland watershed source area by surface alterations (e.g., ditches, roads, terraces, irrigation) does not impact wetland, and NO subsurface alterations within a 1/4 mile (e.g., tile drains, ditches, irrigation wells).

Surface alterations of upland watershed source area impacts overland flow into wetland (e.g., ditches, roads, terraces, irrigation, etc.), however , no subsurface alterations(e.g., tile drains, irrigation wells).

Indicator:

Subsurface Impacts are between 1320 and 900 feet AND 3 feet or greater in elevation below the wetland bottom. Surface impacts reduce effective catchment by 25 percent OR an increase of up to 125 to the catchment.

Upland watershed source area is changed to alter the dominant surface (26 to 50 percent and subsurface flow path (899 to 500 feet away AND 3 feet or greater in elevation below the bottom of the wetland) of water to the wetland(e.g., draining or irrigation return or draw-down).

-AND-

Alteration does not change the NWI classification.

 

Upland watershed source area (25 percent or less is intact) is changed to alter the dominant surface flow path of water to the wetland (e.g., draining or irrigation return or draw-down).

-AND-

Alteration does change the NWI classification.

Upland watershed source area extremely altered such that almost all water flow to wetland eliminated (e.g., urbanization).

1.0

 

 

 

0.75

 

 

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

  

2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: Surface outlet, subsurface drain or fill impacts ground water surface elevations and maintenance of saturated anaerobic conditions throughout the wetland. Additionally, outlets provide vectors for the transport of elements and compounds to off-site aquatic

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

  

2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: Land use in the wetland affects soil organic matter content, vegetation, and detrital biomass that results in characteristic removal, conversion, and release of elements and compounds.

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

  

2.0 REMOVAL, AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC: The amount of sediment in the basin impacts the capacity of the wetland to maintain saturated anaerobic conditions throughout the wetland.

 

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

1.0

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

0.25

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

 

2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vbuffer: Buffer Zone

DEFINITION: Land use condition and average width of the buffer zone adjacent to the wetland.

LOGIC: The width and condition of an intact buffer influences the spreading of surface and subsurface flow and increases water contact time in the buffer which helps limit direct inputs of particulate and dissolved elements and compounds.

 

 

Vigorous Well managed grassland OR idle grassland

Hayland OR

average man- aged grassland

Over-utilized OR poorly managed

grassland

 

Alfalfa/Grass

 

 

Alfalfa only

 

Buffer

Condition

Buffer Area

 

0 0.1 0.3 0.5 0.7 0.9 1.0

 

 

0 0.1 0.2 0.4 0.6 0.7 0.8

 

 

0 0 0.2 0.3 0.4 0.5 0.6

 

 

0 0.1 0.1 0.2 0.3 0.3 0.4

 

 

0 0 0.1 0.1 0.1 0.2 0.2

 

0 to 3 3 to 10 10 to 20 20 to 30 30 to 40 40 to 4747 to 50

 

 

Buffer Area = Average buffer width X % continuity

  

2.0 REMOVAL, CONVERSION AND RELEASE OF ELEMENTS AND COMPOUNDS
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic: Upland land use impacts infiltration, the evapo-transpiration process and the potential availability of elements and compounds that influence the quantity and quality of groundwater flow to the wetland.

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

1.0

 

0.75

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

0.0

  3.0 RETENTION OF PARTICULATES

DEFINITION: Deposition and retention of inorganic and organic particulates from the water column, primarily through physical processes.

Effects On-Site: Sediment deposition in Sandhill Depressions is a natural geologic process that is maintained over thousands of years. Natural rates of accumulation are slow. The presence of sediments and the processes that follow result in characteristic soils, hydrology, and geochemistry.

Effects Off-Site: Reduces potential export of particulates to down-gradient wetland and aquatic ecosystems and groundwater systems.

Discussion of Function

Retention applies to particulates arising from both on-site and off-site sources, but excludes in situ production of peat. The retention of particulates function contrasts with the retention, conversion and release of element and compounds function because the emphasis is more dependent on the physical processes (e.g., sedimentation and particulate removal). For example, sediment retention occurs through burial and chemical precipitation (e.g., removal of phosphorous by Fe+++). Dissolved forms may be transported as particles after undergoing sorption and chelation (i.e., heavy metals mobilized with humic and fulvic compounds). Imported sediment can undergo renewed pedogenesis on site, which potentially involves weathering and release of elements that were previously inaccessible to mineral cycling(Brinson 1995).

 3.0 INDEX OF FUNCTION: Retention of Particulates

IF CLOSED DEPRESSION*1:

= (1.0*2 +Vupuse + Vsed + Vbuffer)/4

 

IF NON-CLOSED DEPRESSION:

= (Vhydalt + Vwetuse + Vupuse + Vsed + Vbuffer)/5

*1 – Closed depression is one with no artificial surface water outlet (i.e. surface drain, tile inlet or pump

*2 – The 1.0 in the closed depression formula addresses hydrology(surface outlet variable). If the 1.0 "no outlet" factor is not included, a non-closed depression may show a higher function than an analogous closed depression.

Discussion of Variables

The variables associated with the performance of this function focus primarily on components of the system that affect the physical processes of particulate removal and sedimentation. Particulate removal is dependent upon an undisturbed water column. The variable (Vhydalt) captures the presence/absence of an outlet and the extent of impact it has on the water level. The variable (Vwetuse) captures the extent of disturbance that may resuspend particulate matter within the water column. Sedimentation is represented by direct evidence (Vsed), or by indirect evidence of potential sources via land use activities (Vupuse). For example, Adomaitis et al. (1967) found that an aeolian mixture of snow and soil from surrounding fields without vegetation yielded nearly twice as much sediment as that deposited into native prairie. In addition, the condition, continuity, and width of a buffer around the wetland influences the amount of particulates delivered to the wetland. The impact of a buffer is reflected by the (Vbuffer) variable. 

3.0 RETENTION OF PARTICULATES
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic: None to moderate disturbance of the prairie yields the least particulates delivered to the wetland by water and/or wind.

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

1.0

 

0.75

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

0.0

 

3.0 RETENTION OF PARTICULATES
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC: The amount of sediment in the basin affects the capacity of the wetland to retain particulates.

 

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

1.0

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

0.25

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

 

3.0 RETENTION OF PARTICULATES
Model Variable Measurement or Condition Index
Vbuffer: Buffer Zone

DEFINITION: Land use condition and average width of the buffer zone adjacent to the wetland.

LOGIC: The width and condition of an intact buffer influences the spreading of surface and subsurface flow and increases water contact time in the buffer which helps to limit direct inputs of particulates.

 

 

 

Vigorous Well managed grassland OR idle grassland

Hayland OR

average man- aged grassland

Over-utilized OR poorly managed

grassland

 

Alfalfa/Grass

 

 

Alfalfa only

 

Buffer

Condition

Buffer Area

 

0 0.1 0.3 0.5 0.7 0.9 1.0

 

 

0 0.1 0.2 0.4 0.6 0.7 0.8

 

 

0 0 0.2 0.3 0.4 0.5 0.6

 

 

0 0.1 0.1 0.2 0.3 0.3 0.4

 

 

0 0 0.1 0.1 0.1 0.2 0.2

 

0 to 3 3 to 10 10 to 20 20 to 30 30 to 40 40 to 4747 to 50

 

 

Buffer Area = Average buffer width X % continuity

  

3.0 RETENTION OF PARTICULATES
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: If an outlet is present, changes in outlet elevation and amount of fill can affect the degree to which particulates will be retained or exported.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

  

3.0 RETENTION OF PARTICULATES
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: If an outlet is present, wetland land use determines the degree to which particulates are retained or exported due to roughness and anchoring of soil by roots and plant cover.

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

 4.0 MAINTENANCE OF CHARACTERISTIC PLANT COMMUNITY

DEFINITION: Characteristic plant communities are not dominated by exotic or nuisance species. Vegetation is maintained by mechanisms such as seed dispersal , seed banks, and vegetative propagation which respond to variations in hydrology and disturbances such as fire and herbivores. The emphasis is on the temporal dynamics and structure of the plant community as revealed by species composition and abundance.

Effects On-Site: Creates microclimatic conditions that support the life histories of plants and animals. Converts solar radiation and carbon dioxide into complex organic carbon that provides energy to drive food webs . Provides habitat for feeding, and cover for nesting, resting refuge, escape, and breeding for resident and migratory animals.

Effects Off-Site: Provides a source of vegetative propagules for adjacent ecosystems which assists in revegetation following drought or disturbance and provides for gene flow between populations. Provides habitat for animals from adjacent ecosystems and for migrating birds (waterfowl, waders, etc.).

Discussion of Function:

Vegetation accounts for most of the biomass of prairie wetland systems. The physical characteristics of living and dead plants are closely related to eco-system functions associated with hydrology, nutrient cycling, and the abundance and diversity of animal species (Lillie and Evard 1994). Vegetation is not static however, and species composition and physical characteristics can change in space and time in response to natural and anthropogenic influences (Weller 1987).

The vegetation in the prairie pothole temporary (wet meadow) and seasonal (shallow marsh) wetlands changes both inter- and intra-annually due to regional climatic cycles and its effect on local hydrological regime (Weller 1987, Kantrud 1989, Kantrud et al. 1989). Variable precipitation and evapotranspiration commonly lead to years of extended drought or above normal moisture. Cyclic vegetation patterns arise from these climatic conditions. Much of the variability is explained by Stewart and Kantrud (1972).

4.0 INDEX OF FUNCTION: Maintain Characteristic Plant Community

={Vwetuse + Vpratio +[Vsorpt + Vpcover + Vdetritus +(Vsed + Vhydalt)/2]/4}/3

Discussion of Variables:

The variables within this functional index address plant community characteristics and potential anthropogenic disturbance.

Plant community characteristics are alter by various types of perturbation. The ratio of native to non-native plant species (Vpratio) indicates the health of a plant community. A healthy plant community is comprised of a high percentage of native non-invasive plants. As a system becomes perturbed, invasive native and non-native species out-compete sensitive native species. Plant abundance, as measured by percent cover (Vpcover), captures the ability of the system to remain self-sustaining. Detritus (Vdetritus) maintains thermal regulation of rhizomes and propagules, and is essential for nutrient cycling. Organic matter in the sandy soil (Vsorpt) holds nutrients and increases water supplying capacity for plant growth.

The elements of a healthy plant community may be compromised by anthropogenic activities. Land use within the wetland (Vsed, Vwetuse) directly impacts plant communities by burying or disrupting detritus, seed banks, rhizomes, etc. Finally, hydrophytic plants are directly affected by water level and soil moisture regime which may be affected by the presence of an outlet. The presence and degree of impact of an outlet and source area is reflected in the (Vhydalt) variable.  

4.0 maintain characteristic plant community
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: Disturbance in the wetland can have an influence on the maintenance of native plant populations.

 

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

  

4.0 Maintain characteristic plant community
Model Variable Measurement or Condition Index
Vpratio: Ratio of Native to Non-native Plant Species

DEFINITION: The ratio of native non-invasive plant species to non-native plus invasive plant species present in wetland zones (Wet Meadow, Seasonal) as indicated by the dominants, using the 50/20 rule, or by a more extensive species survey.

Dominants are the most abundant species that immediately exceed 50% of the total dominance for a given stratum when the species are ranked in descending order of abundance and cumulatively totaled. Dominants also include any additional species comprising 20% or more of the total.

Invasive natives include hybrid and narrowleaf cattail, cocklebur, and trees.

LOGIC: The presence of a high ratio of non-invasive native to invasive native and non-native plant species indicates that disturbances which interrupt naturally occurring cycles and other vegetative dynamics are minimal.

All dominant species in the wetland are native, non-invasive species.

- OR -

76% to 100% of all species found in extensive survey are native, non-invasive species and they dominate the canopy in all zones.

Native, non-invasive species comprise 75% to 99% of the dominants.

- OR -

>50% to 75% of all species found are native, non-invasives and the dominate the canopy in all zones.

Native, non-invasive species comprise 50% to 74% of the dominants.

- OR -

>26 to 50% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 40% of the wetland’s canopy.

Native, non-invasive species comprise 25% to 49% of the dominants.

- OR -

>10 to 25% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 20% of the wetland’s canopy.

Native, non-invasive species comprise less than 25% of the dominants, or less than 10% of all species found by an extensive species survey.

- OR -

Lythrum salicaria (Purple loosestrife) is among the dominants.

 

Vegetation is virtually eliminated by extreme disturbance such as intensive feedlot use.

1.0

 

 

 

 

 

0.75

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

 

 

 

0.0

  

4.0 Maintain characteristic plant community
Model Variable Measurement or Condition Index
Vsorpt: Soil Sorptive Properties for loamy sand and loamy fine sand textures

DEFINITION: The ability of the upper part of the soil to retain and move elements and compounds.

LOGIC: In sandy soils, organic matter content increases water and plant nutrient holding capacity.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NOTE: See appendix for soils with SL and FSL textures.

Organic Matter is >2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a neutral hue with a value of 2 or 3.

-OR-

The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of <=3 and chroma of <2 and lacks a darker-colored A horizon immediately or contiguously below 6 inches.

-OR-

Site has no evidence of drainage or excessive vegetation removal

 

Organic Matter is 0.5 to =<2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >3 to <=4 and chroma of <=2.

-OR-

Site has been partially drained and/or there is evidence of intermittent or past cropping or excessive vegetation removal.

 

Organic Matter is <0.5% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >4 AND/OR chroma of >2.

-OR-

Site has been "effectively" drained and frequently cropped.

Wetland soil has been replaced by upland fill, asphalt, concrete, etc.

1.0

 

 

 

 

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

0.0

 

4.0 Maintain characteristic plant community

Model Variable Measurement or Condition Index
Vpcover: Plant Cover Vegetation covers the ground and is dominated by perennial hydrophytes on >95% of the wetland area, vegetation is not suppressed by tillage, spraying, severe livestock overuse, or other problems. 1.0

 

 

Definition: The typical inter- and intra-seasonal abundance of woody and herbaceous plants in all vegetation zones within the wetland. Vegetation covers the ground and is dominated by perennial hydrophytes on 66% to 95% of the wetland area.

- OR -

Wetland perennial vegetation is slightly thinned by livestock overuse.

0.75

 

 

 

 

Logic: Characteristic plant densities of native prairies influence a suite of plant community components:

seed/rhizome source, nutrient cycling processes, micro-climate conditions, etc.

 

Vegetation covers the ground and is dominated by perennial hydrophytes on 41% to 65% of the wetland area.

- OR -

Perennial hydrophyte vegetation is severely thinned by livestock overuse.

- OR -

Wetland is sometimes tilled or sprayed, but long-term average annual growth of weeds and/or crop achieves 100% canopy.

 

0.5

  Vegetation covers the ground and is dominated by perennial hydrophytes on 20% to 40% of the wetland area.

- OR -

Wetland is frequently tilled or sprayed but average annual growth of weeds and/or crop achieves 75% to 99% canopy cover.

 

0.25

  Vegetation covers the ground and is dominated by perennial hydrophytes on >1% to 19% of wetland area.

- OR -

Wetland is intensively cultivated or sprayed most years, most weed growth is suppressed and total crop growth average is only fair.

 

0.1

  Vegetation is virtually absent due to extreme effects such as continuous feedlot use.

 

 

0.0

 

4.0 maintain characteristic plant community
Model Variable Measurement or Condition Index
Vdetritus: Detritus

DEFINITION: The typical inter and intra-seasonal amount of dead plant material in several stages of decomposition.

LOGIC: Detrital biomass impacts nutrient cycling processes and disturbance regime (e.g., fire) and thereby influences plant assemblages. Detrital cover buffers soil temperature which affects propagule survival.

Temporary Zone - .75 to 2.5 inches

Seasonal Zone --- 2.25 to 6.25 inches

Temporary Zone - .5 to .75 inch -OR- >2.5inches

Seasonal Zone --- 1.5 to 2.25 inches -OR- >6.25 inches

Temporary Zone - .25 to .5 inches

Seasonal Zone --- .75 to 1.5 inches

Temporary Zone - .1 to .25 inches

Seasonal Zone --- ..25 to .75 inches

Temporary Zone - >0 to .1 inches(trace)

Seasonal Zone --- >0 to .25 inches

Litter absent

1.0

0.75

 

0.5

 

0.25

 

0.1

 

0.0

  

4.0 maintain characteristic plant community
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC: Land use and erodibility characteristics of the soil affect the potential for sediment delivery to the wetland. The amount of sediment delivered to the basin impacts the capacity of the wetland to maintain native plant populations.

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

1.0

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

0.25

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

 

4.0 maintain characteristic plant community
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: Surface outlet, subsurface drain or fill impacts ground water surface elevations, and thereby controls the assemblage of aquatic-/nonaquatic vegetation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

 5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND

DEFINITION: Soil, vegetation, and other aspects of the ecosystem structure within a wetland are required by animals for feeding, cover, and reproduction.

Effects On-Site: Habitat provides potential feeding, cover, and reproductive sites for resident and migratory fauna.

Effects Off-Site: Provides feeding, cover, and reproductive sites for resident and migratory fauna and contributes to the matrix or complex that animals require during life cycles.

Discussion of Function:

This function indicates the suitability of vegetation structure, microtopography, and hydrologic conditions for sustaining animal populations. Habitat components (1) provide potential feeding, resting, and nesting sites for vertebrates and invertebrates ; (2) regulate and moderate fluctuations in temperature; and (3) provide habitat heterogeneity to support a diverse assemblage of organisms. Since structure is an important habitat component for resident and nonresident animals, communities possessing a greater structural complexity often are more diverse and species-rich. If intensive studies of wildlife and animal communities are needed and justified, the Habitat Evaluation Procedure (HEP) should be used (U.S. Fish and Wildlife Service 1980).  

5.0 INDEX OF FUNCTION: Maintenance of Habitat Structure Within the Wetland

=[Vpcover + Vpratio + Vbuffer + Vdetritus +(Vupuse + Vwetuse + Vsed + Vhydalt)/4]/5

 Discussion of Variables:

Faunal habitat requirements are areas for resting, nesting, feeding, and shelter from predation and thermal stress. The integrity of the system’s vegetation components, which supply the bulk of the faunal habitat requirements, is captured by the following variables: (Vpratio, Vpcover) and Vdetritus). Land use reflects the ability of the wetland to sustain the habitat conditions and is captured by the (Vupuse, Vwetuse, Vsed, and Vhydalt) variables. Finally, many animals nest or feed in the buffer zone surrounding the wetland, therefore, buffer integrity is measured. Buffer integrity is reflected by the buffer variable (Vbuffer). 

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND

Model Variable Measurement or Condition Index
Vpcover: Plant Cover Vegetation covers the ground and is dominated by perennial hydrophytes on >95% of the wetland area, vegetation is not suppressed by tillage, spraying, severe livestock overuse, or other problems. 1.0

 

 

Definition: The typical inter- and intra-seasonal abundance of woody and herbaceous plants in all vegetation zones within the wetland. Vegetation covers the ground and is dominated by perennial hydrophytes on 66% to 95% of the wetland area.

- OR -

Wetland perennial vegetation is slightly thinned by livestock overuse.

0.75

 

 

 

 

Logic: Characteristic plant densities of native prairie influence habitat components (e.g., resting, nesting, and food supply) to support resident and nonresident fauna.  

Vegetation covers the ground and is dominated by perennial hydrophytes on 41% to 65% of the wetland area.

- OR -

Perennial hydrophyte vegetation is severely thinned by livestock overuse.

- OR -

Wetland is sometimes tilled or sprayed, but long-term average annual growth of weeds and/or crop achieves 100% canopy.

 

0.5

  Vegetation covers the ground and is dominated by perennial hydrophytes on 20% to 40% of the wetland area.

- OR -

Wetland is frequently tilled or sprayed but average annual growth of weeds and/or crop achieves 75% to 99% canopy cover.

 

0.25

  Vegetation covers the ground and is dominated by perennial hydrophytes on >1% to 19% of wetland area.

- OR -

Wetland is intensively cultivated or sprayed most years, most weed growth is suppressed and total crop growth average is only fair.

 

0.1

  Vegetation is virtually absent due to extreme effects such as continuous feedlot use.

 

 

0.0

  

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vpratio: Ratio of Native to Non-native Plant Species

DEFINITION: The ratio of native non-invasive plant species to non-native plus invasive plant species present in wetland zones (Wet Meadow, Seasonal) as indicated by the dominants, using the 50/20 rule, or by a more extensive species survey.

Dominants are the most abundant species that immediately exceed 50% of the total dominance for a given stratum when the species are ranked in descending order of abundance and cumulatively totaled. Dominants also include any additional species comprising 20% or more of the total.

Invasive natives include hybrid and narrowleaf cattail, cocklebur, and trees.

LOGIC: The presence of a high ratio of non-invasive native to invasive native and non-native plant species provides seasonally diverse plant community and, thereby, year-round resting, nesting, and food supply for resident and nonresident fauna.

All dominant species in the wetland are native, non-invasive species.

- OR -

76% to 100% of all species found in extensive survey are native, non-invasive species and they dominate the canopy in all zones.

Native, non-invasive species comprise 75% to 99% of the dominants.

- OR -

>50% to 75% of all species found are native, non-invasives and the dominate the canopy in all zones.

Native, non-invasive species comprise 50% to 74% of the dominants.

- OR -

>26 to 50% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 40% of the wetland’s canopy.

Native, non-invasive species comprise 25% to 49% of the dominants.

- OR -

>10 to 25% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 20% of the wetland’s canopy.

Native, non-invasive species comprise less than 25% of the dominants, or less than 10% of all species found by an extensive species survey.

- OR -

Lythrum salicaria (Purple loosestrife) is among the dominants.

 

Vegetation is virtually eliminated by extreme disturbance such as intensive feedlot use.

1.0

 

 

 

 

 

0.75

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

 

 

 

0.0

  

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vbuffer: Buffer Zone

DEFINITION: Land use condition and average width of the buffer zone adjacent to the wetland.

LOGIC: The condition and width of an intact wetland/upland ecotone influences the availability of food sources for aquatic fauna (e.g., terrestrial invertebrates and upland seeds for vertebrates).

 

 

 

 

 

Vigorous Well managed grassland OR idle grassland

Hayland OR

average man- aged grassland

Over-utilized OR poorly managed

grassland

 

Alfalfa/Grass

 

 

Alfalfa only

 

Buffer

Condition

Buffer Area

 

0 0.1 0.3 0.5 0.7 0.9 1.0

 

 

0 0.1 0.2 0.4 0.6 0.7 0.8

 

 

0 0 0.2 0.3 0.4 0.5 0.6

 

 

0 0.1 0.1 0.2 0.3 0.3 0.4

 

 

0 0 0.1 0.1 0.1 0.2 0.2

 

0 to 3 3 to 10 10 to 20 20 to 30 30 to 40 40 to 4747 to 50

 

 

Buffer Area = Average buffer width X % continuity

  

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vdetritus: Detritus

DEFINITION: The typical inter and intra-seasonal amount of dead plant material in several stages of decomposition.

LOGIC: Characteristic detrital biomass within the wetland offers year round habitat components (e.g., resting, nesting, and food supply) that support characteristic numbers of non-resident and resident fauna especially invertebrates.

Temporary Zone - .75 to 2.5 inches

Seasonal Zone --- 2.25 to 6.25 inches

Temporary Zone - .5 to .75 inch -OR- >2.5inches

Seasonal Zone --- 1.5 to 2.25 inches -OR- >6.25 inches

Temporary Zone - .25 to .5 inches

Seasonal Zone --- .75 to 1.5 inches

Temporary Zone - .1 to .25 inches

Seasonal Zone --- ..25 to .75 inches

Temporary Zone - >0 to .1 inches(trace)

Seasonal Zone --- >0 to .25 inches

Litter absent

1.0

0.75

 

0.5

 

0.25

 

0.1

 

0.0

 

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic: Upland land use affects species that are interdependent on both wetland and upland habitat.

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

1.0

 

0.75

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

0.0

 

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: Land uses in the wetland affect habitat features directly through alteration of vegetation composition, horizontal and vertical structure, and native plant and invertebrate populations.

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

  

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC: Sediment delivered to the wetland affects the capacity of the wetland to maintain native faunal populations, especially invertebrates.

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

1.0

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

0.25

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

  

5.0 MAINTENANCE OF HABITAT STRUCTURE WITHIN WETLAND
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: Surface outlet, subsurface drain or fill impacts ground water surface elevations, thereby impacting the performance of water storage and maintenance of aquatic-habitat conditions throughout the wetland.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

  

MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS

DEFINITION: The spatial relationship of an individual wetland with respect to adjacent wetlands in the complex.

Effects On-Site: The assessed wetland contributes to habitat features of the wetland complex by virtue of its position in the landscape.

Effects Off-Site: Contributes to overall landscape diversity of habitat for aquatic and terrestrial organisms.

Discussion of Function:

Wetlands provide water and other life requirements for motile species that primarily exploit upland habitats. In addition, all vegetative strata in wetlands, from herbaceous layer to tree canopy, provide wildlife corridors (connections) between different wetland types, between uplands and wetlands, and between uplands(Sedell et al. 1990). Such connections between habitats help maintain higher animal and plant diversity across the landscape than would be the case if habitats were more isolated from one another (Brinson 1995).

6.0 INDEX OF FUNCTION: Maintenance of Habitat Interspersion and Connectivity among Wetlands

={[(Vupuse+(((Vwetuse+Vhydalt)/2)+Vbuffer)/2)/2]*[(Vwbasin+(Vwdistance + Vwdistribution + Vwdiversity + Vwlandscape)/4)/2]}1/2

 Discussion of Variables:

Uninterrupted corridors are critical for movement of animals within and between wetlands. The integrity of these corridors may be disturbed through human-induced perturbations both within and around the assessment area. The extent of these perturbations is represented by the variables (Vupuse, Vwetuse, and Vhydalt). (Vupuse) represents the land use within the watershed above the wetland, (Vwetuse) represents land-use within the wetland, and (Vhydalt) represents the maintenance of water level within the wetland and alterations which impact this maintenance. The buffer influences the cover and movement of organisms within and between wetlands. The buffer is represented by the (Vbuffer) variable.

The Vwbasin, Vwdistance, Vwdistribution, Vwdiversity and Vwlandscape variables reflect the density, distance, and pattern of different types of wetlands in the landscape, and their contribution to habitat. Land use conditions within a radius of one mile and its contribution to habitat quality is reflected in the landscape variable.

Sandhill depressional wetlands are a dynamic, integrated system that provides habitat for migratory ducks and geese. If a wetland is accessible and provides a high quality food source, waterfowl will seek it out. Waterfowl dynamics as they are related to wetland types are explained in Gersib et al. (1989). 

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic: Upland land use affects species that are interdependent on both wetland and upland habitat.

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

1.0

 

0.75

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

0.0

   

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC: Land uses in the wetland affect habitat features directly through alteration of vegetation composition, horizontal and vertical structure, and native plant and invertebrate populations.

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

 

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic: Surface outlet, subsurface drain or fill impacts ground water surface elevations, thereby impacting the performance of water storage and maintenance of aquatic habitat conditions throughout the wetland.

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

  

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vbuffer: Buffer Zone

DEFINITION: Land use condition and average width of the buffer zone adjacent to the wetland.

LOGIC: : The condition and width of an intact wetland/upland ecotone influences the availability of food sources for aquatic fauna (e.g., terrestrial invertebrates and upland seeds for vertebrates).

 

 

 

 

 

 

Vigorous Well managed grassland OR idle grassland

Hayland OR

average man- aged grassland

Over-utilized OR poorly managed

grassland

 

Alfalfa/Grass

 

 

Alfalfa only

 

Buffer

Condition

Buffer Area

 

0 0.1 0.3 0.5 0.7 0.9 1.0

 

 

0 0.1 0.2 0.4 0.6 0.7 0.8

 

 

0 0 0.2 0.3 0.4 0.5 0.6

 

 

0 0.1 0.1 0.2 0.3 0.3 0.4

 

 

0 0 0.1 0.1 0.1 0.2 0.2

 

0 to 3 3 to 10 10 to 20 20 to 30 30 to 40 40 to 4747 to 50

 

 

Buffer Area = Average buffer width X % continuity

   

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vwbasin: Number of Basins in the Landscape

DEFINITION: The number of wetland basins on the landscape within a defined radius from the WAA. (Data reported at 1/4 mile scale).

LOGIC: There is more perimeter in several small basins than one large basin of equal area. Edge is a key factor to the faunal guild.

 

 

5 or more wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 80 wetland basins)

4 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 64 wetland basins)

3 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 48 wetland basins)

2 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 32 wetland basins)

1 wetland basin within one mile radius from the center of assessment wetland.

No other wetlands within 1 mile radius.

 

1.0

 

 

0.75

 

0.5

 

0.25

 

0.1

 

0.0

 

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vwdistance: Distance to Semi-permanent or Wetter

DEFINITION: The distance from the edge of the assessed wetland to the nearest semi-permanent or wetter wetland, in feet.

LOGIC: Many vertebrate species are dependent on surface water. The proximity of surface water is correlated to the usefulness of the landscape by faunal guilds.

Less than 660 feet (less than 1/8 mile)

 

 

660 feet to 1320 feet.(between 1/8 to1/4 mile)

 

 

1320 feet to 2640 feet.(between ¼ to ½ mile)

 

2640 feet to 5280 feet.(between ½ to 1 mile)

 

5280 feet to 10540 feet.(between 1 to 2 miles)

 

>10540 feet.(greater than 2 miles)

1.0

 

 

0.75

 

 

0.5

 

0.25

 

0.1

 

0.0

   

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vwdistribution: Wetland Distribution on the Landscape

DEFINITION: A measure of the similarity of the wetland distribution on the assessed wetland’s landscape compared to the well-distributed complex that reflects high quality habitat.

LOGIC: Location of wetlands in proximity to each other facilitates biota migration/transfer from one basin to another. Optimum distribution differs for various natural processes, such as disease confinement, territorial breeding behavior, or genetic transfer. [ To maintain natural wetland distribution quality in the complex at a particular geographic location, any mitigation creation should maintain a spatial distribution similar to the wetland being mitigated for.]

Wetlands within a mile radius are present on an area comprising a contiguous block of > 60%.

-OR-

Wetlands within a mile radius are absent on an area comprising a contiguous block of < 40%.

Wetlands within a mile radius are present on an area comprising a contiguous block of 10 to 60%.

-OR-

Wetlands within a mile radius are absent on an area comprising a contiguous block of 40 to 90%.

 

Wetlands within a mile radius are concentrated within a block that comprises less than 10% of the area.

 

No other wetlands present within the mile radius of evaluated area.

 

 

1.0

 

 

 

 

0.5

 

 

 

 

 

0.1

 

 

0.0

   

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
Vwdiversity: Diversity of Wetland Water Regimes

DEFINITION: A measure of the diversity of wetland water regimes found within ¼ mile radius of the center of the assessed wetland. (i.e., PEMA, PEMC, PEMF).

LOGIC: Studies show that the water regimes exhibited by the three major Palustrine wetland classes are beneficial for meeting vertebrate and invertebrate needs during phases of their life cycle.

 

Temporary, seasonal and semi-permanent or wetter present.

(PEMA, PEMC and PEMFor PABF)

Temporary and semi-permanent or wetter present

-OR-

Seasonal and semi-permanent or wetter present

Temporary and seasonal present

 

Only seasonal present

-OR-

Only semipermanent or wetter present

Only temporary present

 

No wetlands present

1.0

 

 

0.75

 

 

0.5

 

0.25

 

 

0.1

 

0.0

  

6.0 MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
V wlandscape: Perennial Vegetation in the Landscape

DEFINITION: The native prairie and other perennial vegetation that is managed for primary or secondary wildlife use present within a mile radius of the center of the assessed wetland.

LOGIC: The amount of native prairie or other perennial vegetation that is managed for primary or secondary wildlife use within a mile radius of the assessed wetland edge indicates the amount of suitable corridors, dispersal area, and faunal range of the community.

 

Landscape surrounding the wetland is >75% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is 25 to 75% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is 10 to 25% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is made up of <10% annual plants or perennial vegetation that is managed for primary or secondary wildlife use.

 

1.0

 

 

0.50

 

 

0.25

 

 

0.1

 

 

 

 

  

1.0 INDEX OF FUNCTION: Maintain Characteristic Hydrology

={Vhydalt * [(Vsource + Vupuse + Vsed)/3 + (((Vsorpt +Vpore)/2) + Vwetuse)/2]/2}1/2

={______ x [(_______ + ______ + ____)/3 + (((______ + _____)/2)+_______)/2]/2}1/2

 

2.0 INDEX OF FUNCTION: Removal, Conversion and Release of Elements and Compounds

=[Vsorpt + Vpore + Vpcover + Vdetritus +(Vsource + Vhydalt)/2 + (Vwetuse + Vsed + Vbuffer + Vupuse)/4]/6

=[______ + _____+ _______ + ________ + (_____ _+ _______)/2 + (_______ + ____ + _________ + _______)/4]/6

 3.0 INDEX OF FUNCTION: Retention of Particulates

IF CLOSED DEPRESSION*1:

= (1.0*2 +Vupuse + Vsed + Vbuffer)/4

= (1.0 + _______ + _____ + ______)/4

IF NON-CLOSED DEPRESSION:

= (Vhydalt + Vwetuse + Vupuse + Vsed + Vbuffer)/5

= (_______ + _______ + ______ + ____ _ + ______)/5

*1 – Closed depression is one with no artificial surface water outlet (i.e. surface drain, tile inlet or pump

*2 – The 1.0 in the closed depression formula addresses hydrology(surface outlet variable). If the 1.0 "no outlet" factor is not included, a non-closed depression may show a higher function than an analogous closed depression.

4.0 INDEX OF FUNCTION: Maintain Characteristic Plant Community

={Vwetuse + Vpratio +[Vsorpt + Vpcover + Vdetritus +(Vsed +

Vhydalt)/2]/4}/3

={________ + _____ + [______ + _______ + ________ +(____ +

_______)/2]/4}/3

5.0 INDEX OF FUNCTION: Maintenance of Habitat Structure Within the Wetland

=[Vpcover + Vpratio + Vbuffer + Vdetritus +(Vupuse + Vwetuse + Vsed + Vhydalt)/4]/5

=[_______ + ______ + ______ + ________ +(_______ + _______ + _____ + ______)/4]/5

 6.0 INDEX OF FUNCTION: Maintenance of Habitat Interspersion and Connectivity among Wetlands

={[(Vupuse+(((Vwetuse+Vhydalt)/2)+Vbuffer)/2)/2]*[(Vwbasin+(Vwdistance + Vwdistribution + Vwdiversity + Vwlandscape)/4)/2]}1/2

={[(_______+(((_______+______)/2)+_______)/2)/2]*[(_______+(_________ + ____________ + __________ + ___________)/4)/2]}1/2

  

Field Guide for Measurement of Indicators and Condition

A PROCEDURE FOR ASSESSMENT

ENDOSATURATED DEPRESSIONAL WETLANDS

ON MLRA 65 NEBRASKA SANDHILLS

INTRODUCTION: This guide is meant to be user friendly and taken to the field to assess the functional capacity of wetlands on the Sandhills in Major Land Resource Area 65 in Nebraska and South Dakota. It is a tool to use to determine minimal effect and the mitigation requirements associated with the projected loss of a wetland or some of its function. This interim model is also a tool that can be used to evaluate wetland use and management alternatives in the conservation planning process.

Before using this field guide a person should become familiar with the preceding functional profile and model explanation parts of this interim model. Reviewing the preceding parts of this model will help determine if this interim model is applicable to the subclass of the wetland to be assessed. This model is intended to be userfriendly.

The following sections in this Field Guide are: Guidelines for Assessing Wetland Function, Tools for Functional Assessment, Preferred Order of Assessing Variables, Detailed Instructions on Measurements of Indicators, and data recording procedures.(See Section IV, Appendix 1, Part B - Figure 1 and 2 for Scale of Assessment and Observation of Variables)

Prior to proceeding with the office review of the functional assessment, an initial review of the project or site proposal needs to be done to fully understand the reason for doing the functional assessment and the scope of assessment needed.  

B. GUIDELINES FOR ASSESSING WETLAND FUNCTIONS

OFFICE PREPARATION:

1. Review the tools list and assure needed tools are available to do the assessment.

2. Prior to performing the office review, it is important to collect the documents and information that is relevant to the site. Pay particular attention to the land use of the assessment site noting any differences in land use within or surrounding the wetland.

Gather and record information on variables Vwbasin, Vwdistance, Vwdistribution, Vwdiversity, Vwlandscape, Vsource and Vhydalt in the office. Prepare the tools needed for the field assessment. Take recorded comments and data to the field with you.

 FIELD ASSESSMENT:

Bound the Assessment Area in the Field by:

a. Separate upland from wetland

Separate HGM wetland subclasses on the project site into Wetland Assessment Areas(WAA)

c. Separate disturbance regimes

Walk the perimeter of the wetland

Look for buffer, outlet, source intercept, sediment delivery and verify variables assessed in the office.

b. Verify bounding of Wetland Assessment Area(WAA).

c. Look for representative areas to assess variables in temporary and seasonal zones.

d. Visually determine zones and confirm when plant, soils and hydrology data is gathered.

Guide to help in estimating % area of circular zones:

% Radial distance(center to edge) 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

center pointà .--------)--------)--------)--------)--------)--------)---------)---------)--------)--------)

% Area within that radius 1% 4% 9% 16% 25% 36% 49% 64% 81% 100%

3. Follow the steps for on-site measurement of indicators in the field as explained in the Preferred Order of Assessing Variables and the Detailed Instructions for Determination and Measurement of Indicators.

4. Score the variable index scores on worksheet Table A-1 along with measurements and comments.

5. Calculate Functional Capacity Index’s(FCI’s) using Table A-2 or computer program.

6. Check to insure you have all needed field data collected and recorded. Review the data collected to see if it makes sense and recheck data appearing questionable.

TOOLS FOR FUNCTIONAL ASSESSMENT

 OFFICE TOOLS:

USGS QUAD MAPS

NWI WETLAND MAPS

PHOTO MAPS OF WETLAND AND THE AREA WITHIN ONE MILE RADIUS

METHOD/TOOLS FOR ACREAGE CALCULATION

SOIL SURVEY

MAP SCALE 

FIELD TOOLS:

INTERIM FUNCTIONAL ASSESSMENT MODEL NEBRASKA SANDHILLS

PHOTO MAP OF WETLAND AND LANDSCAPE

BASIC SURVEY EQUIPMENT; HAND, ABNEY OR TRANSIT LEVEL, ROD, SURVEY OR STADIA

PLANT IDENTIFICATION HANDBOOKS

CAMERA, FILM, TRIPOD, ETC.

SPADE, SOIL PROBE OR AUGER FOR SOILS WORK

HAND LENS

CLIPBOARD, PAPER, PEN-PENCIL

FIELD RECORDING SHEETS

SOIL SURVEY

SOILS FIELD KIT - SPATULA, ACID, MUNSELL COLOR BOOK, TAPE MEASURE, WATER BOTTLE, HYDRIC SOIL INDICATORS BOOK,

FLAGS - VARIOUS COLORS OR LATH AND FLAGGING TAPE

MARKING PENS (TO WRITE ON FLAGS)

100 FOOT CHAIN

ACREAGE SCALE/RULER

CALCULATOR WITH SQUARE ROOT CAPABILITY

TILE PROBE

OTHER CONSIDERATIONS:

NOTIFY OWNER/OPERATOR

INSECT REPELLENT

SUN SCREEN

WADERS, HIP-CHEST-IRRIGATION

BINOCULARS

GENERAL LAND USE KNOWLEDGE OF THE BASIN

M.A.R.S.H. PLANT ID PROGRAM IN A LAPTOP

GPS PLGR

BAGS AND CARDBOARD OR PLANT PRESS FOR PLANT COLLECTIONS

EDTA SOLUTION

PREFERRED ORDER OF ASSESSING VARIABLES

1. Vwbasin

When approaching the wetland(s), examine area within 1320 feet(1/4 mile) radius, verify location of wetlands found in office review and a route to wetland basins noted as suspect. Formulate plans for an on-site check if needed (For larger wetlands a 1 mile radius may be needed to accurately assess the Vwbasin variable).

2. Vwdistance

The measurement of this variable is the distance in feet from the assessed wetland to the nearest semi-permanent or wetter wetland in any direction, measured edge to edge. When verifying office data, note any changes that affect the measurement of the nearest semi-permanent or wetter wetland. If changes are made based on field observation, make adjustments to measurement of this variable.

3. Vwdistribution

The measurement of this variable is the similarity of the wetland distribution on the assessed landscape, within a 1 mile radius of the assessed wetland’s center, compared to the well distributed complex that reflects high quality habitat conditions. When verifying office data, note any changes that affect the measurement of this variable. If changes are made based on field observation, make adjustments to measurement of this variable.

4. Vwdiversity

The measurement of this variable is the diversity of wetland water regimes within a ¼ mile radius of the center of the assessed wetland. When verifying office data, note any changes that affect the measurement of the diversity. If changes are made based on field observation, make adjustments to measurement of this variable.

5. Vwlandscape

The measurement of this variable is the percent of the landscape, within a mile radius of the center of the assessed wetland, that is native prairie and/or other perennial vegetation which is managed for primary or secondary wildlife use. When verifying office data, note any changes in permanent vegetation or management. If changes are made based on field observation, make adjustments to measurement of this variable.

6. Vsource

Review USGS quad sheets of the area, noting the watershed. Observe and note drainage work (ditches, subsurface drains) in and outside of the wetland and within 1/4 mile of the wetland. Eyeball the subject wetland and note land use and any alterations such as drains or tile, watershed size and any source impacts such as roads, irrigation, etc. Also note any indicators of high water marks such as trash lines, detritus hanging in standing vegetation, sediment stains, etc.

7. Vsorpt

Using soil survey tools, locate wetland edge and wetland zones. Observe hydric indicators, soil color, organic matter levels, evidence and effectiveness of drainage, and evidence and frequency of cropping.

8. Vpore

Using soil survey tools, locate wetland edge and wetland zones. Within the wetland look for an Ap horizon or other evidence of tillage, plow pan, and horizontally deflected roots. Observe soil structure, soil pores and rupture resistance.

9. Vhydalt

Using survey equipment, establish the following elevations: Wetland bottom, natural threshold outlet, constructed outlet, any wetland zones, hydric line, high water. Estimate average depth. Observe and note drainage work (ditches, subsurface drains) in and outside of the wetland and within 500 feet of the wetland. Determine amount of fill in the wetland. Record any length, width or other measurements you feel are appropriate.

10. Vpcover - Vpratio

Survey plant populations; species and abundance, canopy, and note any noxious plants.

11. Vsed

Check sediment depth and record representative depths and the amount of the area of the wetland affected by sediment. Also consider the past and present surrounding land use and erosion.

12. Vdetritus

Measure thickness of litter in both the temporary and seasonal zone if present. Variability will dictate the number of measurements to be taken to obtain a representative thickness.

13. Vbuffer

Observe the upland within 50 feet of the wetland. Use best professional judgment in determining average width and land use condition of the buffer.

14. Vupuse - Vwetuse

Observe and record the dominant land use within the wetland and the dominant land uses within ¼ mile radius of the wetland perimeter. (Note: If wetland is divided by significantly different uses, separate assessments may be needed —See Bounding)

E. DETAILED INSTRUCTIONS FOR DETERMINATION AND MEASUREMENT OF

INDICATORS

Where to Measure: Vwbasin

This variable assesses the actual number count of wetland basins on the landscape within ¼ mile radius of the center of the assessed wetland.

When to Measure:

The data for this variable can be gathered in conjunction with the variables Vwdistance, Vwdistribution, Vwdiversity and Vwlandscape and initially is done in the office. Always verify results in the field.

What and How to Measure:

In the office, review the NWI and FSA wetland inventory maps and inscribe circles scaled to ¼ mile and 1 mile radius from the center of the assessed wetland. Aerial color slides and other photography may also be helpful. Count the number of wetlands within or intercepted by the inscribed circle. Verify the number count in the field. (For larger wetlands a radius of 1 mile (2000.3 acres) may be needed to describe the Vwbasin variable). If a wetland is bisected by a road, count it as one wetland.

When approaching the site on the field review, verify presence and location of wetlands found in office review of the area within the 1/4 mile radius (1320 feet). Formulate plans for an on-site check if needed.

What to Record:

Number of wetland basin(s) within ____ mile radius of the center of the assessed wetland _____________.  

Model Variable Measurement or Condition Index
Vwbasin: Number of Basins in the Landscape

DEFINITION: The number of wetland basins on the landscape within a defined radius from the WAA. (Data reported at 1/4 mile scale).

LOGIC:

 

 

5 or more wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 80 wetland basins)

4 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 64 wetland basins)

3 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 48 wetland basins)

2 wetland basins within ¼ mile radius from the center of assessment wetland. (1 mile radius 32 wetland basins)

1 wetland basin within one mile radius from the center of assessment wetland.

No other wetlands within 1 mile radius.

 

1.0

 

 

0.75

 

0.5

 

0.25

 

0.1

 

0.0

 Where to measure: Vwdistance

The distance from the edge of the assessed wetland to the nearest semi-permanent or wetter wetland in the landscape is captured by this variable. The measurements are made from the boundary edge of the wetland being assessed to the nearest boundary edge of the semi-permanent or wetter wetland in any direction in the landscape.

When to measure:

Distance measurements for this variable can be made while gathering the data for Vwbasin, Vsource, Vhydalt, Vwlandscape. Vwdistribution and Vwdiversity. The initial measurement is easily done in the office and verified in the field.

How and what to measure:

Identify the assessed wetland on NWI and/or FSA wetland inventory maps. On a scaled map, measure the edge to edge distance between the assessed wetland and the closest semi-permanent or wetter wetland found in any direction. Record the distances in feet.

WHAT TO RECORD:

Distance to the nearest semi-permanent or wetter wetland __________.    

Model Variable Measurement or Condition Index
Vwdistance: Distance to Semi-permanent or Wetter

DEFINITION: The distance from the edge of the assessed wetland to the nearest semi-permanent or wetter wetland, in feet.

LOGIC:

Less than 660 feet (less than 1/8 mile)

 

 

660 feet to 1320 feet.(between 1/8 to1/4 mile)

 

 

1320 feet to 2640 feet.(between ¼ to ½ mile)

 

2640 feet to 5280 feet.(between ½ to 1 mile)

 

5280 feet to 10540 feet.(between 1 to 2 miles)

 

>10540 feet.(greater than 2 miles)

1.0

 

 

0.75

 

 

0.5

 

0.25

 

0.1

 

0.0

 Where to measure: Vwdistribution

The measurement of this variable is the similarity of the wetland distribution on the assessed landscape, within a 1 mile radius of the assessed wetland’s center, compared to the well distributed complex that reflects high quality habitat conditions.

When to measure:

Measurements for this variable can be made while gathering the data for Vwbasin, Vsource, Vhydalt, Vwlandscape. Vwdistance and Vwdiversity. The initial measurement is easily done in the office, but field verification is needed.

How and what to measure:

Use the NWI and/or FSA wetland maps to locate the assessed wetland and inscribe a circle scaled to a 1 mile radius around its center. Visually estimate the size of a contiguous block where wetlands are present or absent within the 1 mile radius on the map. Map work observations will need to be verified in the field.

wlizap.gif (5261 bytes)


WHAT TO RECORD:

Percent of contiguous area within a 1 mile radius that has a presence or absence of wetlands.

Presence __________. Absence ___________.  

Model Variable Measurement or Condition Index
Vwdistribution: Wetland Distribution on the Landscape

DEFINITION: A measure of the similarity of the wetland distribution on the assessed wetland’s landscape compared to the well-distributed complex that reflects high quality habitat.

LOGIC:

Wetlands within a mile radius are present on an area comprising a contiguous block of > 60%.

-OR-

Wetlands within a mile radius are absent on an area comprising a contiguous block of < 40%.

Wetlands within a mile radius are present on an area comprising a contiguous block of 10 to 60%.

-OR-

Wetlands within a mile radius are absent on an area comprising a contiguous block of 40 to 90%.

 

Wetlands within a mile radius are concentrated within a block that comprises less than 10% of the area.

 

No other wetlands present within the mile radius of evaluated area.

 

 

1.0

 

 

 

 

0.5

 

 

 

 

 

0.1

 

 

0.0

  Where to measure: Vwdiversity

The measurement of this variable is the diversity of Palustrine wetland water regimes (Cowardin Classification System) within a ¼ mile radius of the assessed wetland.

When to measure:

Measurements for this variable can be made while gathering the data for Vwbasin, Vsource, Vhydalt, Vwlandscape, Vwdistance and Vwdistribution. The initial measurement is easily done in the office, but field verification should be done.

How and what to measure:

Use the NWI maps to locate the assessed wetland and inscribe a circle scaled to a ¼ mile radius. Visually observe and record the different water regimes (Palustrine – Cowardin Classification System Classes) present within the ¼ mile radius. Consult with the FSA Wetland Inventory Map for wetlands currently present on the landscape and verify in the field.

WHAT TO RECORD:

List the different wetland water regimes present. ___________________________________.  

 
Model Variable Measurement or Condition Index
Vwdiversity: Diversity of Wetland Water Regimes

DEFINITION: A measure of the diversity of wetland water regimes found within ¼ mile radius of the center of the assessed wetland. (i.e., PEMA, PEMC, PEMF).

LOGIC:

 

Temporary, seasonal and semi-permanent or wetter present.

(PEMA, PEMC and PEMFor PABF)

Temporary and semi-permanent or wetter present

-OR-

Seasonal and semi-permanent or wetter present

Temporary and seasonal present

 

Only seasonal present

-OR-

Only semipermanent or wetter present

Only temporary present

 

No wetlands present

1.0

 

 

0.75

 

 

0.5

 

0.25

 

 

0.1

 

0.0

 Where to Measure: Vwlandscape

The measurement of this variable is the percent of the landscape within a mile radius of the center of the assessed wetland that is native prairie and other perennial vegetation which is managed for primary or secondary wildlife use.

When to Measure:

This variable is most conveniently measured in the office using recent aerial photography. A land use or recent soil map may provide the needed land use information. Verify the land use in the field. This measurement can be made while gathering the data for Vwbasin, Vsource, Vhydalt, Vwdistance, Vwdistribution and
Vwdiversity

How and What to Measure:

Use a recent land use map, soil map or NWI map to locate the assessed wetland and draw a circle scaled to a 1 mile radius around its center. Measure the acreage of native prairie plus other perennial vegetation that is managed for primary or secondary wildlife use. This percentage can be estimated except where there is some doubt about which index category best represents the area, then use a dot counter or planimeter to measure the area.

What to Record: Measurement(s):

Percent of native prairie or other perennial vegetation that is managed for primary or secondary wildlife use ____________.

MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS
Model Variable Measurement or Condition Index
V wlandscape: Perennial Vegetation in the Landscape

DEFINITION: The native prairie and other perennial vegetation that is managed for primary or secondary wildlife use present within a mile radius of the center of the assessed wetland.

LOGIC:

Landscape surrounding the wetland is >75% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is 25 to 75% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is 10 to 25% percent native prairie or other perennial vegetation that is managed for primary or secondary wildlife use.

Landscape surrounding the wetland is made up of <10% annual plants or perennial vegetation that is managed for primary or secondary wildlife use.

 

1.0

 

 

0.50

 

 

0.25

 

 

0.1

 

 

 

 

 Where to measure: Vsource

This variable reflects the catchment area and the groundwater source area. Measurement of this variable will be from the wetland out to 1/4 mile from the wetland.

 When to measure:

These measurements can be taken at any time during the assessment, but for efficiency, they could be done in the office and checked in the field. If small wetlands on flatter topography do not show contour lines on the USGS maps for delineating catchment area and ground water flow area, sketch on an aerial photo in the field.

How and what to measure:

Review aerial photography, USGS quad sheets, scope and effect maps and NWI maps. Note and document any surface alterations (roads, surface ditches, terraces, etc.), Irrigation systems, and subsurface alterations (tile, wells, etc.) within a ¼ mile radius of the wetland. Note and document wetland subclass. From the USGS quad map, delineate the original catchment area.

NOTE: If the office review can determine that the catchment area has been altered, determine the amount of catchment area that has been structurally altered to prevent flow to the wetland. Also note areas added to the watershed due to road ditches or drainage.

In the field verify all alterations noted during the off-site review and document any additional alteration found during the field investigation.

WHAT TO RECORD:

Type and effect of surface alteration(s) _______________

Type and effect of subsurface alteration(s) _______________

Change in NWI wetland subclass(Yes or No) _______________

Percent catchment area affected _______________
 

Model Variable Measurement or Condition Index
Vsource: Source Area of Flow to Wetland

DEFINITION: The area surrounding a wetland that defines the catchment and groundwater flow area to the wetland.

LOGIC:

Alteration of upland watershed source area by surface alterations (e.g., ditches, roads, terraces, irrigation) does not impact wetland, and NO subsurface alterations within a 1/4 mile (e.g., tile drains, ditches, irrigation wells).

Surface alterations of upland watershed source area impacts overland flow into wetland (e.g., ditches, roads, terraces, irrigation, etc.), however , no subsurface alterations(e.g., tile drains, irrigation wells).

Indicator:

Subsurface Impacts are between 1320 and 900 feet AND 3 feet or greater in elevation below the wetland bottom. Surface impacts reduce effective catchment by 25 percent OR an increase of up to 125 to the catchment.

Upland watershed source area is changed to alter the dominant surface (26 to 50 percent and subsurface flow path (899 to 500 feet away AND 3 feet or greater in elevation below the bottom of the wetland) of water to the wetland(e.g., draining or irrigation return or draw-down).

-AND-

Alteration does not change the NWI classification.

 

Upland watershed source area (25 percent or less is intact) is changed to alter the dominant surface flow path of water to the wetland (e.g., draining or irrigation return or draw-down).

-AND-

Alteration does change the NWI classification.

Upland watershed source area extremely altered such that almost all water flow to wetland eliminated (e.g., urbanization).

1.0

 

 

 

0.75

 

 

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

 Where and When to measure: Vsorpt

The wetland will be scouted and the measurement recorded will be representative for the temporary or seasonal zone assessed in the wetland. The percent of each zone will be recorded. This information will then be used to calculate the index for all or the portion of the wetland that is needed for the assessment. These measurements can be recorded when checking for sediment or detritus thickness.

How and What to measure:

Upon examining the soils and the wetland basin, note the evidence and effectiveness of drainage (not drained, partially drained, and effectively drained), and evidence of cropping and frequency of cropping. An "effectively" drained wetland still exhibits some wetland character which does not interfere with cropping most years.

With the use of a spade(sharpshooter) take a vertical slice of soil to a depth of 16 inches. Examine in good sunlight. This should be done when the soil is moist and not when wet or dry. Wet soils glisten which interferes with reading colors. If sampling site is under water, the use of a soil probe (preferably one with a 1.5" diameter coring tube) could be used to obtain a sample.

Using the Munsell Soil Color Chart, examine the colors of the A horizon from the surface to 6 inches. Record the hue, chroma and value. (Note; check for Neutral Colors in the A horizon and note whether there is a darker-colored A horizon below and contiguous to the A in the upper 6 inches.)

List the hydric soil indicator used to identify the hydric soil if found in the Field Indicator of Hydric Soils Publication. If EDTA is used for determining the level of soil organic matter, use the field method outlined by R.A. Bowman, USDA-ARS, Akron, CO.

WHAT TO RECORD: Temporary Zone Seasonal Zone

Percent of total wetland area: ________________ __________________

Indicators:

Evidence and effectiveness of drainage: _________________ ___________________

Evidence and frequency of cropping: ____________________ ___________________

Soil Color:

Hue:__________________________________________

Chroma:   ______________________________________

Value: ________________________________________

Darker A Horizon contiguous (Yes or No)_________________ ___________________

below 6 inches

Texture of A horizon within 6 inches: ____________________ ___________________

Texture of A horizon below 6 inches: ____________________ ___________________

Measurement:

Percent Organic Matter(EDTA Method): __________________ ___________________

  

Model Variable Measurement or Condition Index
Vsorpt: Soil Sorptive Properties for loamy sand and loamy fine sand textures

DEFINITION: The ability of the upper part of the soil to retain and move elements and compounds.

LOGIC:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NOTE: See appendix for soils with SL and FSL textures.

Organic Matter is >2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a neutral hue with a value of 2 or 3.

-OR-

The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of <=3 and chroma of <2 and lacks a darker-colored A horizon immediately or contiguously below 6 inches.

-OR-

Site has no evidence of drainage or excessive vegetation removal

 

Organic Matter is 0.5 to =<2.0% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >3 to <=4 and chroma of <=2.

-OR-

Site has been partially drained and/or there is evidence of intermittent or past cropping or excessive vegetation removal.

 

Organic Matter is <0.5% (Measurement) for loamy sand and loamy fine sand textures.

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of >4 AND/OR chroma of >2.

-OR-

Site has been "effectively" drained and frequently cropped.

Wetland soil has been replaced by upland fill, asphalt, concrete, etc.

1.0

 

 

 

 

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

0.0

 Where to measure: Vpore

The wetland will be scouted and the measurement recorded will be representative for the temporary or seasonal zone assessed in the wetland. This information will then be used to calculate the index for all or the portion of the wetland that is needed for the assessment.

When to measure:

These measurements can be taken anytime during the assessment, but for efficiency, could be performed in conjunction with the delineation procedure. These measurements can be recorded when checking for soil organic matter, sediment or detritus thickness.

How and what to measure:

In assessing this variable look for micro-topographical highs and lows in the wetland that may be associated with past evidence of tillage.

With the use of a spade(sharpshooter) take a vertical slice of soil to a depth of 16 inches. Examine in good sunlight. Apply a moderate thud to the back of the spade to help show the natural structure cleavage of the soil. Record presence or absence of an Ap horizon or evidence of past tillage.

Pay special notice to the 4 to 10 inch layer checking for a plow pan. Note, look in the 4 to 10 inch depth range for horizontal layer(s) or plate like structure which could be a plow layer. Look for root growth deflected horizontally as an indicator of a highly compacted layer (plow pan) Record findings.

Examine the slice and note the size, shape and grade (distinctness) of the soil peds in the A horizon. Note if the structure parts to moderate, medium and fine granular and the size of blocks. Record the size, grade, and type of structure for the A horizon. If sampling site is under water the use of a soil probe (preferably one with a 1.5" diameter coring tube) could be used to obtain a sample, however, coarser structure and grade of structure may not be evident.

Examine horizontal surfaces for tubular(non-matrix) pores. Concentrate on the layer with the least amount of pores and the most compaction if an Ap is present. Count the number of very fine and fine pores in a square centimeter and the number of medium and coarse pores in a square decimeter and record. Also examine the pores to determine their continuity. Record the number of pores and their continuity. Note: Roots are a surrogate for pores.

To determine rupture resistance in the upper 16 inches of the soil, take a soil ped (about 1 inch cube) that has not been compressed or deformed in getting the slice and crush it between your forefinger and thumb, noting the strength needed to deform or rupture the ped. Note this estimation as very friable(very slight force), friable(slight force), firm(moderate force) or very firm(strong force). Then record the most resistant measurement found within the upper 16 inches. (Hint; If tilled this will probably be in a 4 inch thick layer found just below the tillage zone which may extend to 12 inches below the surface.)

WHAT TO RECORD: INDICATORS:

Evidence of past tillage: Temp Zone (yes or no)_______ Seas Zone (yes or no) _______

Ap horizon present: Temp Zone (yes or no)_______ Seas Zone (yes or no) _______

Plow pan with roots growing

horizontally along pan: Temp Zone (yes or no) ____ Seas Zone (yes or no) _______

SECONDARY MEASUREMENTS:

Soil Structure: Temporary zone Seasonal zone

Size: _______________ _________________

Type: _______________ _________________

Grade: _______________ _________________

Soil Pores:

Number: _______________ _________________

Continuity: _______________ _________________

Rupture

Resistance: _______________ _________________

  

Model Variable Measurement or Condition Index
Vpore: Soil Porosity

DEFINITION: The ability of the soil to allow movement of liquids, gases, etc. into, and through, the upper part of the soil as indicated by the physical integrity of the upper part of the soil. This includes the number and continuity of pores, the type, grade, and size of soil structure, and the soils rupture resistance.

 

LOGIC:

 

 

 

 

 

 

Note: Direct Measurement of Vpore is Soil infiltration / permeability measurements in the upper 12" of the soil. No standards set at this time.

 

Secondary Measure - The upper (12") soil horizons structure, i.e. the A1 weak or moderate granular structure. The A2 has weak subangular blocky parting to weak or moderate granular structure.

Many very fine and fine, continuous pores.

Rupture resistance is very friable.(very slight force)

Indicator - No evidence of an Ap within hydric soil boundary.

Secondary Measure - Weak subangular blocky and/or weak granular structure -and/or- Medium and coarse plate-like structure below the plow layer.

Common very fine and fine, continuous and discontinuous pores.

Rupture resistance is friable.(slight force)

Indicator - Ap horizon is present. Wetland is partially tilled or restored (cropland) < 20 years

Secondary Measure - Massive or coarse subangular blocky -and/or- Strong coarse plate-like structure (coarse, cloddy)below Ap horizon.

-AND-

Rupture resistance is friable to firm.(slight to moderate force) Few very fine and fine discontinuous pores.

Indicator - Plow pan evidenced by roots growing horizontally along pan. Ap horizon present. Wetland is tilled throughout most years.

The substrate is a non-porous medium, i.e., asphalt, concrete, etc.

1.0

 

 

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

0.0

 Where and When to measure: Vhydalt

This variable will be measured from the bottom (lowest elevation) of the wetland out to five hundred feet from the wetland boundary. Elevation shots will be taken at the lowest elevation of the wetland, at the control section of the outlet (highest point of a natural outlet or a man made outlet), at the wetland boundary, and depth of drainage features in relation to wetland elevations.

These measurements can be taken anytime during the assessment, but for efficiency, could be performed in conjunction with the delineation procedure. Distances to drainage features may be measured from aerial photography prior to going to the field.

How and what to measure:

Elevations and distances will be determined by approved surveying methods and equipment. Hydrology alterations are typically in the form of lateral removal of subsurface flow or saturation, surface water removal and / or fill placed in the wetland.

Preferred method:

Lateral Removal of Subsurface Flow

1. Elevations of buried subsurface drainage features (tile) should be determined as follows:

a. Determine the tile size from scope & effect or local information.

b. Determine the shortest distance between the tile and the wetland.

c. Determine the depth the tile is below the ground surface with the tile probe.

d. Shoot the elevation at this location and subtract the depth to tile and the tile diameter from the g
round elevation.

2. Elevations of surface drainage features (road ditches, etc.) should be determined as follows:

Determine the shortest distance between the surface drainage feature and the wetland.

Shoot the elevation of the lowest point in the surface drainage feature at this  distance.

Surface Water Removal

a. Shoot the elevation of the surface outlet (natural or man made).

b. Shoot the elevation of the wetland bottom.

c. Compare the two elevations to determine if site ponds water.

Fill Placed in Wetland

Using the methods described in Vsed, determine if fill has been placed in the wetland by digging or probing in the wetland to determine if wetland has been filled.

WHAT TO RECORD:

Distance to surface drainage feature _______________

Distance to subsurface drainage feature _______________

Depth of surface drainage feature _______________

Depth of subsurface drainage feature _______________

Diameter of subsurface drainage feature _______________

Elevation of surface outlet _______________

Elevation of wetland bottom _______________

Depth of ponding _______________

Depth of fill _______________

 

Model Variable Measurement or Condition Index
Vhydalt Hydrology Alterations

Definition: Presence of a constructed subsurface and/or surface outlet affecting the wetland or fill affecting the depth of the wetland.

Logic:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: If state approved methods for calculating lateral effects of subsurface drainage are available they may be used in place of the above scaling for subsurface effects only.

Surface drain or subsurface drain has no effect on wetland. Surface drain or subsurface drain is > 500 feet from the wetland edge and less than 3 feet below the wetland bottom elevation. If surface drain is present and within 500 feet of wetland, it is at or above the top of the temporary zone in elevation. No fill in wetland.

Surface drain or subsurface drain 200 to 500 feet from outside wetland edge and greater than 3 feet below wetland bottom elevation.

-OR-

Surface outlet invert lowered to remove some static storage.

-OR-

Wetland filled to reduce 50 percent of the static storage.

Wetland still ponds water.

Surface outlet is present which removes all static water or subsurface drain is within 200 feet of wetland edge and drain is greater than 3 feet below wetland elevation bottom.

-OR-

If large wetland, tile spacing is greater than 300 feet or ineffectively removing saturated conditions.

-OR-

Site filled to the top of the temporary zone with some saturation remaining in wetland.

Wetland meets saturation criteria only.

Surface outlet is below bottom of wetland, and subsurface drain 3 feet or greater below wetland bottom elevation with spacing less than 300 feet in all parts within the wetland.

-OR-

Wetland filled eliminating saturated conditions in the wetland.

1.0

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

 

0.0

 

 

 WHERE TO MEASURE Vpcover:

This variable will be measured within each wetland zone present (temporary and seasonal) and the findings will be recorded. The information will be used to assign an index score that is representative for the assessment area.

When to measure:

This variable can be measured at any time the vegetation is visible, but knowledge of long-term conditions on the site is the key to assigning a proper score. Assessing Vpcover and the Vpratio variable concurrently is suggested.

How and what to measure:

The Vpcover evaluation needs to consider both the typical inter-seasonal and intra-seasonal conditions of the wetland. The assigned score needs to represent the average quantity of vegetation that grows on the wetland. The score must also reflect the typical % of the growing season during which the wetland is vegetated. Events such as fire, tillage, extended wet or dry periods, and abrupt changes in precipitation will cause wide fluctuations from the average amount of plant growth. In these cases, seek additional information and use best professional judgment. Document observations from aerial color slides and infra-red photography from the current and previous years, and the knowledge of reliable persons familiar with the site.

Preferred method:

Flag the perimeter of the assessment area. Evaluate the plant cover on the entire assessment area, but not beyond it. Avoid being "thrown off" by tillage lines or other pseudo-boundaries.

Look at the wetland from a high point to identify areas with significantly more or less cover than the predominant situation. Determine the relative size of each such area by visual estimation or by measurement such as pacing, and record findings. Assess the plant cover on each portion individually. Then, a weighted index score can be assigned for the wetland.

Walk through the wetland in a zigzag or cross-sectional pattern that will provide a representative view of the vegetation present on the entire wetland. Keep in mind that the outer points of a straight line transect through a wetland represent a greater proportion of its area. For example, the outer one-fourth of a transect represents 44 % of a round wetland, while the inner one-fourth only represents about 6 % of the total wetland area.

Accurate determination of the proportion of different conditions on the outer portion of a wetland is essential for proper assessment. Refer to guide for determining area of circular zones on page 2.

If the wetland has been cultivated or otherwise disturbed in a manner that reduces vegetative growth, observe the amount of plant matter present on the surface. Using a spade, also check for plant residue and roots below the surface. Root mass is a good indicator of recent years’ vegetative growth. Record observations for each vegetative zone present, (wet meadow and shallow marsh). A mental comparison of the assessment site and a comparable native site in excellent condition is helpful. Wet meadow can produce 4000# of forage per acre annually; shallow marsh can produce 7000# . These production levels require a vigorous sod.

Consider the temporal aspect of vegetative cover. While native wetlands in excellent condition "green up" quickly in spring and are usually covered with growing vegetation for most of the growing season, plant cover on cultivated sites is widely variable. Some wetlands are left idle for years at a time; others have a good crop cover most years; and some are intensively cultivated and compacted, resulting in little growth anytime. Cultivated wetlands are often covered by species that are prone to drowning- an intra-seasonal consideration. Best professional judgment is critical for assigning a representative index score. The proper index score may not correspond to the conditions observed at the time of assessment; written documentation should justify the assigned score for such cases.

Future measurement method:

Temporal growth curves that plot the amounts of vegetation expected to be present on a calendar time line for various management scenarios (crop use, hayland, or grazing) of temporary and seasonal wetlands would be very helpful for assessing Vpcover. No research of this type is known to exist at this time.

WHAT TO RECORD ON THE FIELD DATA FORM:

Fill in each data blank separately for each management zone. Repeat for each zone within the wetland assessment area. Exclude areas outside of a Partial Wetland Assessment Area.

Typical long-term conditions in the zone: Current conditions in the zone:

______% of wetland area ______% of wetland area

______% canopy cover ______% canopy cover

_____________________vegetation type, ________________________vegetation type,

including crops and/or upland invaders including crops and/or upland invaders

Factors causing shift from long-term average, if current conditions differ:____________________________________

Assigned index score for the wetland assessment area__________

 
 

Model Variable

Measurement or Condition Index
Vpcover: Plant Cover Vegetation covers the ground and is dominated by perennial hydrophytes on >95% of the wetland area, vegetation is not suppressed by tillage, spraying, severe livestock overuse, or other problems. 1.0

 

 

Definition: The typical inter- and intra-seasonal abundance of woody and herbaceous plants in all vegetation zones within the wetland. Vegetation covers the ground and is dominated by perennial hydrophytes on 66% to 95% of the wetland area.

- OR -

Wetland perennial vegetation is slightly thinned by livestock overuse.

0.75

 

 

 

 

Logic: Vegetation covers the ground and is dominated by perennial hydrophytes on 41% to 65% of the wetland area.

- OR -

Perennial hydrophyte vegetation is severely thinned by livestock overuse.

- OR -

Wetland is sometimes tilled or sprayed, but long-term average annual growth of weeds and/or crop achieves 100% canopy.

 

0.5

  Vegetation covers the ground and is dominated by perennial hydrophytes on 20% to 40% of the wetland area.

- OR -

Wetland is frequently tilled or sprayed but average annual growth of weeds and/or crop achieves 75% to 99% canopy cover.

 

0.25

  Vegetation covers the ground and is dominated by perennial hydrophytes on >1% to 19% of wetland area.

- OR -

Wetland is intensively cultivated or sprayed most years, most weed growth is suppressed and total crop growth average is only fair.

 

0.1

  Vegetation is virtually absent due to extreme effects such as continuous feedlot use.

 

 

0.0

 Where to measure Vpratio:

This variable will be measured within each wetland zone present (temporary and seasonal) and the findings will be recorded. The information will be used to assign an index score that is representative for the assessment area.

When to measure:

These observations can be made at any time during the assessment. Observing and recording Vpcover and Vpratio data concurrently is suggested, for efficiency.

How and what to measure:

The Vpratio measurement needs to take into account the typical inter-seasonal and intra-seasonal conditions of the wetland. Wetlands that are covered with perennial vegetation are relatively easy to rate. Wetlands that are cultivated intermittently may be more difficult to assess. Events such as fire, tillage, extended wet or dry periods, and abrupt changes in precipitation can change the species composition on part or all of a wetland. In these cases, seek additional information and use best professional judgment. Document observations from aerial color slides and infra-red photography from the current and previous years, and the knowledge of reliable persons familiar with the site.

After extended high-water conditions, a draw-down phase may enable numerous early-succession species to germinate. This may result in a wetland having a very good native community to appear to fit an index score lower than it deserves. A sound understanding of recent conditions and plant succession may justify assigning an index score that does not match the plant community found at the time of assessment. Document the rationale for such cases.

Preferred method:

Flag the perimeter of the assessment area. Evaluate the plants on the entire assessment area, but not beyond it. Avoid being thrown off by tillage lines or other pseudo-boundaries.

If the wetland has a seasonal zone, flag its boundary. Look at the wetland from a high point to identify areas with significantly different vegetation types. Determine the relative size of each such area by visual estimation or by measurement such as pacing, and record findings. Examine the plants on each portion individually. Then, a weighted index score can be assigned for the wetland.

Walk through each vegetative zone of the wetland in a zigzag or cross-sectional pattern that will provide a representative view of the vegetation present. Keep in mind that the outer points of a straight line transect through a wetland represent a greater proportion of its area. For example, the outer one-tenth of a transect represents 19% of a round wetland, while the inner 10% represents only 1% of the total wetland area. Accurate determination of the proportion of different conditions in the wetland is essential for proper assessment. Refer to page 2 guide for determining proportion of circular zones.

Considering the expected growth for the entire season, estimate the % of total vegetation mass that the dominant species will produce in each zone present, (wet meadow and shallow marsh). Keep in mind that warm-season species such as Prairie cordgrass and yellow foxtail are slow starters with rapid growth later. Growth measurement could be done by weighing clipped samples late in the growing season, but is not rapid. At other times, the decision must be based on Best Professional Judgment, with knowledge of the growth capabilities of the each species. Record observations on a data sheet. After assigning % of total production to the dominants in each zone, look over the wetland again to mentally check if the assigned proportions are reasonable. Make adjustments if needed.

After determining which species comprise the dominants in each zone, classify them as native or non-native. Then assign the appropriate Vpratio index score. NOTE: While only the dominant species need to be evaluated for Vpratio, it is desirable to base the Vpratio measurement on an extensive species survey.

What to record on the field data sheet:  

List of all species found in the wetland by extensive species survey________________

Cumulative % of the canopy that is comprised by non-invasive native species______________

% of canopy that is Purple loosestrife, if any________

- OR -

_______% of the total vegetative cover comprised by each of the dominant species________(list each).

_______% of vegetative cover, if any, that is Purple loosestrife.

Assigned Vpratio index score__________ Remarks on plant succession factors or rationale for the assigned Vpratio index score, if the assigned score does not match existing conditions_______________________________.

 

 
Model Variable Measurement or Condition Index
Vpratio: Ratio of Native to Non-native Plant Species

DEFINITION: The ratio of native non-invasive plant species to non-native plus invasive plant species present in wetland zones (Wet Meadow, Seasonal) as indicated by the dominants, using the 50/20 rule, or by a more extensive species survey.

Dominants are the most abundant species that immediately exceed 50% of the total dominance for a given stratum when the species are ranked in descending order of abundance and cumulatively totaled. Dominants also include any additional species comprising 20% or more of the total.

Invasive natives include hybrid and narrowleaf cattail, cocklebur, and trees.

LOGIC:

 

 

 

 

All dominant species in the wetland are native, non-invasive species.

- OR -

76% to 100% of all species found in extensive survey are native, non-invasive species and they dominate the canopy in all zones.

Native, non-invasive species comprise 75% to 99% of the dominants.

- OR -

>50% to 75% of all species found are native, non-invasives and the dominate the canopy in all zones.

Native, non-invasive species comprise 50% to 74% of the dominants.

- OR -

>26 to 50% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 40% of the wetland’s canopy.

Native, non-invasive species comprise 25% to 49% of the dominants.

- OR -

>10 to 25% of all species found by an extensive species survey are non-invasive natives and they cumulatively comprise at least 20% of the wetland’s canopy.

Native, non-invasive species comprise less than 25% of the dominants, or less than 10% of all species found by an extensive species survey.

- OR -

Lythrum salicaria (Purple loosestrife) is among the dominants.

 

Vegetation is virtually eliminated by extreme disturbance such as intensive feedlot use.

1.0

 

 

 

 

 

0.75

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

 

 

 

0.0

Where to measure: Vsed

A representative site will be selected by scouting and measurements will be made in both the temporary and seasonal zone of the wetland. This information will then be used to calculate the index for all or the portion of the wetland that is needed for the assessment.

A good question to ask is where is the sediment coming from? Wind-deposited sediment is probably thickest on the northwest, west and south sides of the wetland. Is water-deposited sediment coming from an ephemeral drain or a steep slope? Is there a buffer? Most likely, within the wetland the sediment will be deepest along the outer edge of the temporary zone. Other important items to consider are land use differences if they exist in the catchment area. On oval-shaped wetlands with the thickest sediment, deltas can usually be seen on aerial photos or colored slides, especially if active deltas are forming.

Soil observations along wetland edge can be used to estimate the amount of sediment delivered. Over-thickened A horizons are excellent evidence but must be calibrated to local reference standard A horizon thickness’. Another method of assessing this variable is predictively using a simplified USLE or WEQ approach. (Slopes, Wind Erodibility Groups and Land Use).

When to measure:

These measurements can be taken anytime during the assessment, but for efficiency, could be performed in conjunction with the delineation procedure and when checking for detritus thickness.

How and what to measure:

With the use of a spade(sharpshooter) take a vertical slice of soil to a depth of 16 inches or greater if sediment is expected. Examine in good sunlight. If sampling site is under water the use of a soil probe (preferably one with a 1.5" diameter coring tube) could be used to obtain a sample. In cases where the texture is coarse sand or coarser in texture, a probe may not work and an auger can be used. Sediment usually is harder to detect in an auger sample.

Preferred method:

Use a color difference in the dark colored A horizon to indicate sediment. If a color lighter than value 3 and chroma 2, (ie.10YR 3/2), is found over a darker A horizon, this is a good indicator of sediment. The thickness can be recorded as sediment delivered to the wetland when and if mixing by tillage is weighted.

If the suspected sediment feels more gritty than the underlying material, this can be an indicator of sediment. In this case, fines were removed by wind or water and the coarser material was blown or washed in the wetland, making the sediment feel more gritty.

Alternative Method:

If the thickness of the A horizon is used to indicate the thickness of sediment delivered to the wetland, this should be measured in the temporary zone. Soil observations along wetland edge can be used to estimate the amount of sediment delivered. Over-thickened A horizons are excellent evidence but must be calibrated to local reference standard A horizon thickness’. In MLRA 65, soils such as Tryon and Loup can be studied to determine undisturbed thickness of the A horizon. This is an indirect way and will not work well if the natural lower boundary does not have a contrasting abrupt boundary, but is gradual and diffuse, as which usually happens in the seasonal zone.

WHAT TO RECORD:

Thickness of sediment in temporary zone ___________________

Thickness of sediment in seasonal zone ____________________

Indicators:

Evidence of erosion on surrounding land use ________________

 

 
Model Variable Measurement or Condition Index
Vsed: Sediment Delivered to Wetland

DEFINITION: Extent of sediment delivered to wetland from human disturbance sources, including agriculture.

LOGIC:

 

Little to no evidence of sediment delivery to wetland.

Indicators: No evidence of past or present tillage in the buffer or wetland area. Surrounding upland is native prairie with no observable evidence of erosion.

Representative sediment depth –(Measurement)

temporary zone is <4 inches; seasonal zone is <2 inches

Indicators: Evidence of historic and/or culturally accelerated sediment delivery in the form of stabilized deltas, sediment fans etc. Most of the basin is not affected by sediment. Principal surrounding land use is moderately eroding grassland -OR- cropland that has good residue management and a buffer. None to slight erosion on surrounding croplands. Slopes 2-4%(1/4 mile) No evidence of past or present tillage in the wetland.

Representative sediment depth –(Measurement)

temporary zone is 4 to <6 inches; seasonal zone is 2 to <7 inches

Indicators: Surrounding land use is severely eroded grassland -OR- cropland that has had good residue management and no wetland buffer. About half of the basin is affected by sediment. Evidence of moderate erosion on cropland. Slopes 4-6%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is 6 to <10 inches; seasonal zone is 7 to <12 inches

Indicators: Tillage through buffer into wetland that has had fair residue management on surrounding uplands. Nearly all of the basin affected by sediment. Evidence of severe erosion on surrounding croplands. Slopes 6-9%(1/4 mile).

Representative sediment depth –(Measurement)

temporary zone is =>10 inches; seasonal zone is =>12 inches

Indicators: Evidence of very severe erosion upwind from wetland with recent accumulations of sediment.

-OR-

Wetland filled with sediment but some basin remains

-OR-

A vegetation zone change(i.e. Shallow Marsh to Wet Meadow)

Basin filled and topographic shape of the landscape depression is not evident.

1.0

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

0.25

 

 

 

 

 

 

0.1

 

 

 

 

 

0.0

 Where to measure: Vdetritus

A representative site will be selected by scouting and measurements will be made in both the temporary and seasonal zone of the wetland. This information will then be used to calculate the index for all or the portion of the wetland that is needed for the assessment.

When to measure:

These measurements can be taken anytime during the assessment, but for efficiency it could be performed in conjunction with the delineation procedure or in conjunction with collecting the Vsorpt, Vpore and Vsed variable measurements. (Note: The detritus thickness diminishes as the year passes.)

How and what to measure:

Preferred method:

The index finger can be used to measure the thickness of detritus (undecomposed brown litter or dead plant material) and the thickness noted on the finger can be measured with a ruler and recorded. A slightly gritty or smooth feeling on your finger tip indicates you have gone through the detritus layer. If finger method fails, use of probe or spade is an alternative described below.

Care should be taken not to compact the detritus and not to measure the current year’s growth. Previous years’ growth is what to measure. If different land uses exist in the assessment area, a number of measurements need to be taken and averaged to assign the representative condition of the wetland.

3. Measurement will be recorded in both the temporary and seasonal zones.

Alternate method:

With the use of a spade(sharpshooter) take out a plug of soil deep enough to penetrate beyond the detrital layer. Account for disturbance by compaction, measure and record depth in inches to nearest 1/4 inch(0.1 inch in temporary zone when less than ¼ inch).

If sampling site is under water the use of a soil probe instead of a spade (preferably one with a 1.5" diameter coring tube) could be used to obtain a sample. Compare the cored samples to the detrital mass in the wetland. Coarse or fibrous material may slide around the probe tip. If the core samples do not match their source area, then use other sampling techniques.

WHAT TO RECORD:

Representative thickness of detritus in the Temporary Zone ____________.

Representative thickness of detritus in the Seasonal Zone ____________.

 

 
Model Variable Measurement or Condition Index
Vdetritus: Detritus

DEFINITION: The typical inter and intra-seasonal amount of dead plant material in several stages of decomposition.

LOGIC:

Temporary Zone - .75 to 2.5 inches

Seasonal Zone --- 2.25 to 6.25 inches

Temporary Zone - .5 to .75 inch -OR- >2.5inches

Seasonal Zone --- 1.5 to 2.25 inches -OR- >6.25 inches

Temporary Zone - .25 to .5 inches

Seasonal Zone --- .75 to 1.5 inches

Temporary Zone - .1 to .25 inches

Seasonal Zone --- ..25 to .75 inches

Temporary Zone - >0 to .1 inches(trace)

Seasonal Zone --- >0 to .25 inches

Litter absent

1.0

0.75

 

0.5

 

0.25

 

0.1

 

0.0

 

BUFFER EVALUATION

The buffer area of a wetland is technically part of the upland and not the wetland. The measurement of conditions which become the index score are very subjective as definitive research on buffers and wetlands is not readily available. The indexing is based on common sense, limited literature and best professional judgment. Buffers around wetlands are seldom contiguous, of the same land use, or of uniform width. This is why the evaluator is allowed latitude in making a best professional judgment in index scoring the Vbuffer variable.

WHERE TO MEASURE

This will be an onsite field measurement. Width measurement is outward from the jurisdictional (1987 COE Manual) edge.

WHAT AND HOW TO MEASURE

As buffers are seldom continuous around a wetland edge in only one condition, the evaluator must use some discretionary judgment. This can be done by dividing the wetland and its buffer into pie wedges. Only perennial vegetation will be measured as acceptable buffer cover. Percent continuity and average buffer width will be determined along with the buffer condition. It will be easier to describe how much of the buffer is a particular width or a particular land use. The indexing can then be scored with some mental weighting. The evaluator may also want to consider the amount of watershed which would enter the wetland at a particular point.

EXAMPLE

Consider this simple example. If a wetland is cut off from part of its watershed, but immediately adjacent to a road, the buffer would only be the width of the road slope which would also be the entire watershed from that side. If the other half of the wetland buffer is conventional tillage cropland, and represents the side with dominant watershed contribution, it would be hard to score an index other than conventional tillage, buffer less than 3 feet wide. If the evaluator feels the road slope does play a significant part in wetland functions because it is not mowed or burned and the plants present represent native species, etc., then a somewhat higher index score may be justifiable.

WHEN TO MEASURE

Buffers will have some temporal variation during the year and judgment should be exercised regarding the time of year when measurements are being recorded. The evaluator will be looking for indicators of past use as well as current use. The concern is that buffer could be under-rated too early in the spring, before plants have had a chance to grow, or be credited too much if haying is not taken into consideration.

WHAT TO RECORD

PERCENT CONTINUITIY ___________%

AVERAGE BUFFER WIDTH ____________FEET

WEIGHTED BUFFER CONDITION______________________________.

 

 
Model Variable Measurement or Condition Index
Vbuffer: Buffer Zone

DEFINITION: Land use condition and average width of the buffer zone adjacent to the wetland.

LOGIC:

 

 

 

 

 

 

Buffer Area = Average buffer width X % continuity

Vigorous Well managed grassland OR idle grassland

Hayland OR

average man- aged grassland

Over-utilized OR poorly managed

grassland

 

Alfalfa/Grass

 

 

Alfalfa only

 

Buffer

Condition

Buffer Area

 

0 0.1 0.3 0.5 0.7 0.9 1.0

 

 

0 0.1 0.2 0.4 0.6 0.7 0.8

 

 

0 0 0.2 0.3 0.4 0.5 0.6

 

 

0 0.1 0.1 0.2 0.3 0.3 0.4

 

 

0 0 0.1 0.1 0.1 0.2 0.2

 

0 to 3 3 to 10 10 to 20 20 to 30 30 to 40 40 to 4747 to 50

 WHEN TO MEASURE: Vupuse

Information on present land use is needed to accurately measure and determine the condition of this variable. The land use within ¼ mile radius of the wetland boundary can be checked in the office from land use maps but will be determined in the field. The observation of some land use conditions will vary from season to season, requiring use of Best Professional Judgment during some time periods.

WHERE TO MEASURE:

The variable Vupuse refers to land use within ¼ mile of the wetland boundary. Dominant land use will be noted for the area. If the wetland has a buffer that is managed differently than the rest of the upland, exclude it from this measurement.

WHAT AND HOW TO MEASURE:

This variable considers a disturbance gradient from native prairie to hard surface parking lot. Intensity of tillage, crop types grown, hayland management, grazing management level, amount of bare ground, and amount of native and non-native species present need to be observed.

Information on best management practices will be noted. The amount of disturbance compared to well-managed rangeland will help assure an accurate measurement or assessment of this variable.

Upland land use categories considered in this variable are as follows:

-- Grazed; proper utilization, somewhat over-utilized, or

over-utilized - dominance of native or non-native plant species.

-- Permanent hayland

-- Idle grassland

-- Cropland: type of tillage and types of crops grown

-- Other disturbances described such as feedlot.

WHAT TO RECORD ON VARIABLE SCORE FIELD FORM

For each significant management area (field, pasture, etc) record the following:

Land use__________ comprises _____% of the total upland area. Index score____

Describe the level of management & list Best Mgt Practices in use______________

_______________________________________________________________________

 Weighted index score_______ Additional comments on rationale____________________

 

 
Model Variable Measurement or Condition Index
Vupuse: Upland Land Use

Definition: The most representative land use or management level of the upland within a quarter-mile radius of the wetland’s perimeter.

Logic:

Native prairie managed to allow adequate plant recovery time between vegetation removal.

Dominated by non-native perennial species or native seeding without forbs, with fair management or better.

- OR -

Native species managed under season-long grazing - OR -

Perennially idle grassland cover - OR -

Permanent Hayland

 

Native or non-native species heavily over-grazed, some bare ground, low plant vigor - OR -

No-till continuous high-residue crop

- OR -

Minimum till high-residue crops in a grass/legume rotation

 

Native or non-native species heavily over-grazed, high amounts of bare ground, low plant vigor, and evidence of soil erosion - OR - No-till low-residue or minimum-till high-residue crops

 

Intensive tillage, minimum-till low-residue crops, or similar reduction of vegetation and/or residue.

 

Extremely disturbed site such as feedlot. Condition will result in maximum overland flow and/or high rate of particulate delivery to wetland.

1.0

 

0.75

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

0.0

WHEN TO MEASURE: Vwetuse

Information on past and present land use is needed to accurately measure and determine the condition of this variable. Past or historical land use within the wetland should be checked in the office by viewing current and old land use maps. Other avenues of information for determining past land use would be from the producer, owner, or other reliable persons familiar with the site. Current land use will be determined in the field. The observation of some conditions will vary by season and are subject to Best Professional Judgment during some time periods.

WHERE TO MEASURE:

The variable Vwetuse refers to land use within the jurisdictional boundary of the wetland assessment area. Land use will be noted for both the temporary and seasonal zone if present.

WHAT AND HOW TO MEASURE:

This variable considers a management and use gradient from well-managed native prairie to intensive feedlot use. While most other variables primarily measure existing conditions, this variable measures trend or expected impact on all ecological processes that will result from the management and expected use over a time period that includes dry, normal, and wet years. The assigned score should not be an average of different uses for a wetland in transition from one use to another. Evidence of tillage in the past or present, and its impact in each zone may be needed. Frequency of haying, level of grazing, and evidence of compaction or ruts from machinery or livestock needs to be determined and recorded. The time in years of current and past land uses/changes, if available, can help explain condition. Examining the soil may reveal tillage layers in some cases. Also, the detrital biomass may be a clue to past use.

Land use will be noted in both the temporary and seasonal zone if they differ and as needed to measure or determine the condition of the wetland. Information on the amount of disturbance compared to well-managed rangeland will help assure an accurate measurement or assessment of this variable.

Wetland land use & management level considerations for this variable:

-- Grazed; proper utilization, somewhat over-utilized, and heavily over-utilized

-- Hayed; Frequency, height of stubble, timing

-- Idle

-- Cropland: Type of crops grown, intensity of tillage and pesticide use, irrigation, etc. ---- -- Other disturbances described: Feedlot, excavated pond, parking lot, etc.

WHAT TO RECORD ON VARIABLE SCORE FIELD FORM

Fill in the information blanks for each significant area with different management; i.e., field, pasture, etc.

Typical long-term conditions Current conditions

Temporary zone use ________________ _ Temporary zone use_______________________

conditions/mgt. Level________________ conditions/factors_______________________

Seasonal zone use__________________ Seasonal zone use_________________________

Conditions/mgt. Level_______________ conditions/factors_______________________

Assigned index score________ Additional comments for rationale____________________

 

 
Model Variable Measurement or Condition Index
Vwetuse: Wetland Land Use

DEFINITION: The representative land use and management of the wetland, based on long-term average.

LOGIC:

 

Land use within the wetland & management level should have no adverse impacts such as soil compaction or excessive depletion of plant cover, detritus, or soil organic matter.

Indicator: Wetland is grazed with good or excellent management, or intermittently cut for hay in a timely manner, preventing ruts and allowing secondary use by wildlife.

Management or use of wetland causes slight adverse impacts such as:

- Grazing level slightly suppresses desirable species.

Wetland is cut for hay every year and lacks regrowth for secondary use by wildlife.

Grazing level or haying is causing some compaction or slight reduction in vigor of plants.

 

Management or use of the wetland causes moderately adverse impacts, such as:

Grazing level severely reduces decreaser species. Some trampling or soil compaction may occur.

Hayed wetland is also overgrazed regularly or routinely burned, eliminating most residual cover, and/or moderately reducing plant vigor.

Seasonal wetland is farmed in temporary zone only and shallow marsh zone is idle or properly grazed.

 

Use of wetland causes severe impacts, such as:

Grazing level causes extensive trampling damage and severe thinning of perennial hydrophytes.

Seasonal wetland is usually cropped in temporary zone and seasonal zone is occasionally tilled or sprayed.

 

Use of wetland causes very severe impacts such as:

Wetland is tilled or sprayed in all zones most years.

Wetland is dominated by excavated pond.

 

Adverse impacts are extreme on nearly all of the wetland area, such as intensive feedlot use or >95% excavated for pond.

1.0

 

 

 

 

 

 

0.75

 

 

 

 

 

 

 

0.50

 

 

 

 

 

 

 

 

 

0.25

 

 

 

 

 

0.1

 

 

 

0.0

 

VI . Appendix1

A. Comments on Variables

Vhydalt: All hydrology values except Vsource have been incorporated into the variable Vhydalt. This variable could be split into 2 variables; one to cover surface outlet and filling of the wetland and the other to cover removal of the saturation by Vsubout (tile) adjusted to the proper spacing

Vsorpt: The Vsorpt variable was developed for the Interim HGM Model on depressions in the Lake Dakota Sand Plains. As defined, this variable is applied to the A horizon or upper 6 inches of the soil.

In the Lake Dakota Sand Plains the soils considered are the Rosewood, Venlo, Fossum and Hamar series that are hydric. Other states interested in using this Model are South Dakota and Nebraska. Colors and Organic Matter Levels will need to be checked and adapted as this is applied in the field.

Soil pH is also an indicator of sorptive capacity of soils. May need to develop as a primary indicator, but probably is not easily enough done in a routine Functional Assessment.

Access to and the ability to query the North Dakota Laboratory Data computer database would add credibility and improve the refinement of this variable. Awaiting development of this ability at this time. Other states with Laboratory Data would be of help in adapting these indicators.

The uniformity or pureness of color as described by the salt and pepper effect for the sandy soils is a clue to the organic matter levels of these sandy soils and also to some degree in the loamy and silty textured soils. A change in pureness of color may not be described by color chip, but can be seen with the naked eye. This was noticed when comparing older(10+ years) no-till and grassland soils to annually tilled and cultivated cropland soils.

Ideally, a color index such as the one developed by Illinois would greatly facilitate the use of this variable in the field for sandy hydric soils.

A field method of measuring Soil Organic Matter(SOM) is being looked into. This would allow a quick way to assess SOM in the field for this variable and may provide for more index categories for the Sandhill Interim Model.

The amount of topographic relief is thought to have an impact on this variable. This variable limits local relief to a dominant slope of less than 9%. This can be obtained form the soil survey and checked on site. As the relief increases the amount of sediment from erosion also increases even on well managed native prairie in the sandhills.

 The following Vsorpt variable should be used on moderately coarse surface layers in the Nebraska Sandhills MLRA 65.

Where and When to measure: Vsorpt

The wetland will be scouted and the measurement recorded will be representative for the temporary or seasonal zone assessed in the wetland. The percent of each zone will be recorded. This information will then be used to calculate the index for all or the portion of the wetland that is needed for the assessment. These measurements can be recorded when checking for sediment or detritus thickness.

How and What to measure:

Upon examining the soils and the wetland basin, note the evidence and effectiveness of drainage (not drained, partially drained, and effectively drained), and evidence of cropping and frequency of cropping.

With the use of a spade(sharpshooter) take a vertical slice of soil to a depth of 16 inches. Examine in good sunlight. This should be done when the soil is moist and not when wet or dry. Wet soils glisten which interferes with reading colors and with estimating unstained sand grains. If sampling site is under water the use of a soil probe (preferably one with a 1.5" diameter coring tube) could be used to obtain a sample.

Using the Munsell Soil Color Chart, examine the colors of the A horizon from the surface to 6 inches. Record the hue, chroma and value. (Note; check for Neutral Colors in the A horizon.)

By visual observation (without magnification) record the % of unstained sand grains (salt and pepper effect) in the A horizon from the surface to 6 inches. Soil should be in the moist to slightly dry condition.

List the hydric soil indicator used to identify the hydric soil if found in the Field Indicator of Hydric Soils Publication. If EDTA is used for determining the level of soil organic matter use the field method outlined by R.A. Bowman, USDA-ARS, Akron, CO.

WHAT TO RECORD:

Indicators: Temporary Zone Seasonal Zone

Evidence and effectiveness of drainage: _________________ ___________________

Evidence and frequency of cropping: ____________________ ___________________

Soil Color:

Hue:_______________________ ___________________

Chroma: __________ ________ ___________________

Value: _____________________ ___________________

Percent of unstained sand grains: _______________________ ___________________

Measurement:

Percent Organic Matter(EDTA Method): __________________ ___________________

  

 
Model Variable Measurement or Condition Index
Vsorpt: Soil Sorptive Properties

DEFINITION: The ability of the upper part of the soil to retain and move elements and compounds.

LOGIC:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: For use on the soils with a moderately the coarse surface layer in the Nebraska Sandhills

Organic Matter is >4.0% (Measurement)

Indicators: The mineral soil in all parts of the A horizon within 6 inches of the surface has a value of 2 or 3 and chroma of 0.

-OR-

Value of 2 and chroma of 1 -AND- nearly all sand grains visible to naked eye are coated with organic matter in all parts of the A horizon within 6 inches of the surface.

-OR-

Site has no evidence of drainage or cropping.

 

Organic Matter is 1.5 to =<4.0% (Measurement)

Indicators: The mineral soil in parts of the upper 6 inches or A horizon has a value of >2 to 3 and chroma of 1, or value of 2 and chroma of 2.

-OR-

Value of 2 and chroma of 1 in parts of the A horizon within 6 inches of the surface -AND- Some individual grains of sand are not coated with organic matter, salt and pepper effect is visible.

-OR-

Site has been partially drained and/or there is evidence of intermittent or past cropping.

Organic Matter is <1.5% (Measurement)

Indicators: The mineral soil in the upper 6 inches or A horizon has a value of >3 to 4 and chroma of 1or 2

-OR-

Most individual grains of sand are not coated with organic matter in the A horizon within 6 inches of the surface.

-OR-

Site has been "effectively" drained and frequently cropped.

Wetland soil has been replaced by upland fill, asphalt, concrete, etc.

1.0

 

 

 

 

 

 

 

 

 

0.5

 

 

 

 

 

 

 

 

 

 

 

 

0.1

 

 

 

 

 

 

 

 

0.0

 Vpcover: This variable should measure the amount of living plant matter present on the wetland throughout the growing season and the following dormant season, scaled in comparison to pre-European influence. Vpcover should also be scaled according to the duration of the vegetative cover. The emphasis should probably be on the growing season, when plants trap solar energy, transpire water, produce biomass, and grow roots that enhance soil porosity & organic matter content.

NRCS native hayland production data is a good measure of vegetative production on non-cultivated wetlands, but does not address the temporal gaps that are typical of vegetative cover on cropped wetlands.

Vpratio: This variable is currently scaled to measure only the ratio of native to non-native species in a wetland. The variable needs to serve as a better measure of the quality of the plant community. Three other qualitative factors should also be addressed by the variable: The variable should be scaled to reflect the proportion of the desired species present, similar to the rangeland condition rating system. The variable scaling should also distinguish between invasive, early-succession species and late-succession species. The variable should also address the total diversity of the wetland plant community.

FUTURE MEASUREMENT METHOD: Databases will probably be developed that will enable the computer to determine the Vpratio index score, based on the plant survey done by the assessor. Extensive species surveys would provide a better resource assessment.

Floristic Quality Index (FQI) is a system of evaluating plant communities that may be suitable to replace the current Vpratio index condition or rating categories. FQI will be evaluated in 1999, along with data from a study of 204 northern prairie potholes that was conducted in 1997.

Vwpairs

For areas where Duck Breeding Pair Maps are available, the Vwpairs variable can be substituted for the following variables; Vwlandscape, Vwdistance, Vwdistribution and Vwdiversity in the "MAINTENANCE OF HABITAT INTERSPERSION AND CONNECTIVITY AMONG WETLANDS" function, provided that the number of duck breeding pairs is correctly scaled.

The ¼ or 1 mile radius is inscribed from the center of the assessed wetland; however, if the center radius does not seem appropriate due to wetland size or shape, inscribe the radius from the edge of the assessed wetland.

 B. Field Forms for Data Collection for Functional Assessment

1. Table A-1 Variable Score Field From

a. Stored file(Variascoreff) on floppy disk in Word 7.0

2. Table A-2 Functional Score Field From

a. Stored file (Funcscoreff) on floppy disk in Word 7.0

 

3. Table A-3 Variable Data Worksheet

a. Stored file (Variadataw) on floppy disk in Excel 7.0

Table A-4 Comparison of Wetland Assessment Area and the Mitigation Area

Stored file (MITCHART) on floppy disk in Word 7.0

Table A-5 Relationship of Variables to Wetland Function for

Sandhill Wetlands

Stored file (Prioritychart) on floppy disk in Excel 7.0

C. Explanation of Files Stored on the Computer Disk

(These files are available in electronic form upon request from the Prairie Pothole Wetland Team)

1. Readme.doc

a. Contains an explanation of the following files on the floppy disk.

2. Sandhills HGM Interim Model 1.0.doc

a. This file is in Word 7.0 format, and was developed in Windows 95

This file is a copy of the Sandhills HGM Interim Model. It provides model rationale, function, variable and indicator descriptions for functional assessment of the wetlands in the Nebraska Sandhills of Nebraska and South Dakota.

3. Sandhills HGM.xls

a. This file is in Excel 7.0 format and developed in Msoffice 95

b. This file can be used to calculate FCI,s and FCU’s for the Sandhills Interim Model.

4. Table A-1 Variable Score.doc

a. This file is in word 7.0 on floppy disk

b. This is a field form which can be used to record the Variable score.

5. Table A-2 Functional Score.doc

a. This file is in word 7.0 on floppy disk.

b. This is a field form which can be used to record Functional Score.

 

Table A-3 Variable Data.xls

This file is in Excel 7.0 on floppy disk.

This is a field form which can be used to record pre- and post-activity for wetland functional scoring for more than one wetland along with the corresponding wetland acreage.

7. Table A-4 Mitigation.doc

a. This file is in word 7.0 on floppy disk.

8. Figure 1.doc

a. This file is in Windows 95 - Power Point 7.0

b. This file depicts the different scales at which the wetland is assessed

9. Figure 2.doc

a. This file is in Windows 95 - Power Point 7.0

b. This file depicts the scale at which the variables are assessed 

D. Literature Cited (Existing literature about this model in addition to citations in Northern Prairie Model)

Water Resources #18 by ND State Water Commission

NDSU Oakes Test Area, Bureau of Reclamation

Lee, L. C. and Mark M. Brinson, William J. Kleindl, P. Michael Whited, Michael Gilbert, Wade L. Nutter, Dennis F. Whigham, Dave Dewald. 1997. Operational Draft Guidebook For The Hydrogeomorphic Assessment of Temporary and Seasonal Prairie Pothole Wetlands. Seattle, WA. Pp. 116 + app.

Pytlik, Lea Ann, Quandt, Loyal, Grossman, R. B. 1995. Some Simple Procedures for Field and Field-Laboratory Measurements with Emphasis on the Near Surface. NRCS, NSSC Lincoln NE. Pp. 37

Schulze, Nagel, Van Scoyoc, Henderson, Baumgardner. 1993. Significance of Organic Matter in Determining Soil Colors. SSSA Special Publication no. 31 71-90

Current research on this subject:

Bowman, R. A., W. D. Guenzi, and D. J. Savory. Spectroscopic method for estimation of soil organic matter. Soil Sci. Soc. Am. J. 55:563-566

Derby, N. E. and Knighton R. E. 1995. Depression Focused Recharge and Solute Movement to a Shallow Unconfined Aquifer http://www..soilsci.ndsu.nodak.edu/papers/1995_asa

Derby, N. E., Knighton R. E. and Steele D. D. 1994. Temporal and Spatial Distribution of Nitrate Nitrogen Under Best Management Practices http//www.soilsci.ndsu.nodak.edu/papers/1994_nd

Hopkins, David Glenn, Ph.D., Department of Soil Science, College of Agriculture, North Dakota State University, February 1997. Hydrologic and abiotic constraints on soil genesis and natural vegetation patterns in the sandhills of North Dakota. Ph.D. Thesis.

A USGS – Northern Prairie Wildlife Research Center survey of prairie pothole wetlands conducted in 1997 is unpublished.

 SEND COMMENTS TO: PRAIRIE POTHOLE WETLAND TEAM

       NORTHERN PLAINS REGION, NRCS

       P. O. BOX 1489

       JAMESTOWN, NORTH DAKOTA 58402-1489

       Phone Number: 701-252-2135

http://www.@ndwet@nd.nrcs.usda.gov

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