ORGANIC SOIL FLATS (Indiana) version 1.0

[Interim Wetland Functional Assessment Model]{.underline}

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  **Name**                                              **County**               **Date**        

  **Performed                                                                               
  By**                                                                                      

  **Conversion                                          **Mitigation                        
  Site**                                                Site**                              

  **Farm No.**   **Tract           **Field   **Note**   **Farm No.**   **Tract   **Field    **Note**
                 No.**             No.**                               No.**     No.**      

                                                                                                 

                                                                                                 

                                                                                                 
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This model only applies to wetlands that are similar to the description
as defined in the model. Wetlands that contain rare habitat type,
specifically Red Flag wetlands as defined by the Procedure for Wetland
Minimal Effect Exemptions Indiana cannot be evaluated by this model. Red
Flag wetlands will be inventoried and evaluated to document the wetland
functions and values associated with the wetland including; landform,
hydrology, soils, and plants. Red Flag wetlands can only be mitigated to
a site that can fully replace all functions and values associated with
the wetland under evaluation.

**Subclass Description**

This subclass of wetlands evolved under anaerobic soil conditions due to
saturation and/or ponding. Organic wetlands are found on a variety of
landforms including postglacial lake plains, till plains, outwash plains
or moraines. These wetlands are located primarily in Northern Indiana.
They are distinguished by very low topographic gradients and poorly
drained and very poorly drained organic soils with a surface over 41 cm
thick consisting of organic materials.

The primary water source is precipitation and some wetlands receive
minor overland runoff. These sites typically have high water tables from
fall to early summer. Water tables will fluctuate and are influenced by
evapotranspiration and period rainfall. Surface ponding may be extensive
or may be limited just to micro-depressions within the flat area. Ponded
water typically does not run off laterally. The primary direction of
water movement is vertical in the upper part of the soil profile, but
water movement is horizontal in shallow organic soils which are
underlain by slowly permeable subsoil layers.

This model is based on systems dominated by woody vegetation consisting
of trees and shrubs. The water tables on these site have been lowered
enough to allow woody vegetation to replace the herbaceous vegetation
that would dominate on undisturbed sites. This model can be used where
sites contain trees or shrubs, but it is not intended to be used on
wetland subclasses that are currently dominated by herbaceous wetlands
under normal circumstances.

**Distinguishing Characteristics**

This subclass differs from mineral soil flats in the region in that most
of the mineral wetlands consist of primarily mineral soils and vary in
soil biochemical conditions. The lack of significant surface inflow
distinguishes them from depressional wetlands. The reliance upon
precipitation as opposed to groundwater, and the low topographic
gradient, distinguishes flats from slope wetlands. As opposed to
riverine wetlands, the flats are primarily dependent upon precipitation
with the primary surface water movement being vertical fluctuation as
opposed to unidirectional horizontal flow. In some cases, wetlands in
these other classes may appear similar to flats and may even function
similarly. For example, direct precipitation may be equal to surface
runoff as a primary water source for very large depressional wetlands.
Extensive drainage in the surrounding landscape may have altered the
original hydrologic regimes within the wetlands of this subclass.

**Important Functions**

Due to their flat gradient and fluctuating water tables, the primary
hydrologic function of organic flats is to store subsurface water.
Surface water storage is a minor component and depends upon the amount
of surface ponding. The fluctuating water tables are conducive to rapid
biogeochemical nutrient cycling. Large amounts of organic carbon may be
stored in the herbaceous biomass and organic soils present in mature
ecosystems of this type. These wetlands can occur as a portion of
extensive wetlands which provided important habitat for a variety of
plant and animal species to isolated depression in woods and fields.
Pools within the woods serve as important amphibian breeding sites;
several migratory birds use these as nesting areas.

**[MODEL FUNCTIONS AND VARIABLE LISTING]{.underline}**

[HYDROLOGICAL FUNCTION 1]{.underline} - Water Storage

**Definition**: Capacity of a wetland to temporarily store surface and
sub-surface water for long durations; associated with standing water not
moving over the surface. Sources of water are direct precipitation, and
to a lesser extent, overland flow and lateral subsurface flow.

**Effects On-site**: Replenishes soil moisture; detains water for
chemical transformations; maintains vegetative composition; maintains
seasonally-ponded habitat for herptiles and aquatic invertebrates; and
influences soil characteristics.

**Effects Off-site**: Improves water quality and maintains seasonal flow
distribution.

**Variables**: V~duration,~ V~%\_ponded,~ V~water_table~, V~avail_H2O~

**Index of Function**: (V~duration~ +V~%\_ponded~ + V~water_table~ +
V~avail_H2O)~/4

[BIOGEOCHEMICAL FUNCTION 1]{.underline} - Nutrient Uptake

**Definition**: Abiotic and biotic processes that convert nutrients and
other elements from one form to another; primarily recycling processes.

**Effects On-site**: removes sediments, nutrients, and contaminants; Net
effects of recycling are elemental balances between gains through import
processes and losses through hydraulic export, efflux to the atmosphere,
and long-term retention in persistent biomass and sediments.

**Effects Off-site**: To the extent that nutrients are held on-site by
recycling, they will be less susceptible to export downstream. This
reduces the level of nutrient loading off-site.

**Variables**: V~strata~, V~turnover,~ V~canopy~

**Index of Function**: The lesser of: (V~strata~ + V~canopy~)/2 or
V~turnover~

[BIOGEOCHEMICAL FUNCTION 2]{.underline} - Long-term Storage of Nutrients
and Organic Compounds

**Definition**: The storage of nutrients and organic carbon in the
living and dead biomass above the soil and within the soil profile.

**Effects On-site**: The net effect of carbon storage is long-term
retention in persistent biomass and in organic matter in the soil
profile.

**Effects Off-site**: Nutrients are held on-site and are less
susceptible to transport.

**Variables**: V~basal_area,~ V~turnover,~ V~soil_OM,~ V~snag~

**Index of Function**: (V~basal_area~ +V~turnover~ + V~soil_OM~ +
V~snags~)/4

[HABITAT FUNCTION 1]{.underline} - Maintain Characteristic Plant
Community

**Definition**: Species composition and physical characteristics of
living plant biomass. The emphasis is on the dynamics and structure of
plant community as revealed by the dominant species of trees, shrubs,
saplings, and ground cover, and by the physical characteristics of
vegetation.

**Effects On-site**: Converts solar radiation and carbon dioxide into
complex organic compounds that provide energy to drive food webs.
Provides seeds for regeneration. Provides habitat for nesting, resting,
refuge, and escape cover for animals. Creates micro-climatic conditions
that support completion of life histories of plants and animals.
Provides organic matter for soil development and soil related nutrient
cycling processes. Creates both long- and short- term habitat for
resident or migratory animals.

**Effects off-site**: Provides a source of propagules to maintain
species composition and/or structure of adjacent wetlands and supplies
propagules for colonization of nearby degraded systems. Provides food
and cover for animals from adjacent ecosystems. Provides corridors
(migratory pathways) between habitats, enhances species diversity and
ecosystem stability, and provides habitat and food for migratory and
resident animals.

**Variables**: V~comp~, V~canopy,~ V~strata,~ V~maturity,~ V~turnover~

**Index of Function**: (V~comp~ + V~strata~ + V~turnover~ + V~canopy~ +
V~maturity~)/5

[HABITAT FUNCTION 2]{.underline} - Maintain Wildlife Habitat Structure

**Definition**: The capacity of a wetland to support animal populations
and guilds by providing characteristic habitats.

**Effects On-site**: Provides potential feeding, resting, and nesting
sites for vertebrates and invertebrates. Regulates and moderates
fluctuations in temperature. Provides characteristic habitat to support
a diverse assemblage of organisms dependent upon this wetland type.
Affects all ecosystem processes.

**Effects Off-site**: Provides habitat heterogeneity to landscape,
provides habitat for wide-ranging and migratory animals, provides a
corridor for gene flow between separated populations, and allows progeny
to exploit new areas.

**Variables**: V~%\_ponded,~ V~strata~, V~snags,~ V~maturity~, V~comp~

**Index of Function**: (V~%\_ponded~ + V~snags~ + V~comp~ + V~strata~ +
V~maturity~)/5

[HABITAT FUNCTION 3]{.underline} - Maintain Habitat Interspersion,
Quality, and Connectivity

**Definition**: The capacity for all organisms to be provided with
diverse and contiguous areas of food and cover.

**Effects On-site**: Provides maintenance of habitat, species, and gene
pool diversity.

**Effects Off-site**: Provides habitat heterogeneity to landscape,
provides habitat for wide-ranging and migratory animals, provides a
corridor for gene flow between separated populations, and allows progeny
to exploit new areas.

**Variables**: V~core,~ V~connect,~ V~contiguous_cover~

**Index of Function**: \[(V~contiguous_cover~)2 + V~migrate~ +
V~connect~\]/4

**[WORKSHEETS FOR SCORING WETLAND FUNCTION VARIABLES]{.underline}**

For each of the variables listed below, choose the described condition
that most nearly matches the site under consideration.

[V1 V~duration~]{.underline}

Presence or indication that the wetland surface is ponded for a period
of \>7 days . Possible field indicators of hydrology include (Check all
that apply):

bare soil areas due to inundation

water stained leaves

water rings on trees

obligate hydrophytic vegetation

aerial photography

wrack lines

direct observations

soil Survey Data

A. Four or more indicators are present or direct observation can
document 7 days of ponding. 1.0

B. Three or more indicators are present. 0.75

B. Two indicators are present. 0.50

D. One indicator is present. 0.25

C. Hydrology has been altered to prevent or reduce ponding. Examples 0.1

include evidence of surface ditches, tile drains, and fill. Restoration
is possible.

E. Restoration is not possible to due site constraints. 0.0

[V2 V~%\ ponded~]{.underline}

Variable is scored by measurement or estimate of the extent of ponding
on the wetland surface which indicates ponding for \>7 days. The
variable is also used in Habitat Function #2 as an indicator of canopy
gap.

  ----------------------------------- -----------------------------------
  A. \>50% of area is ponded.         1.0

  B. 10-50% of area is ponded.        0.5

  C. \<10% of area is ponded.         0.1

  D. No evidence of ponding.          0.0
  Restoration not possible            
  ----------------------------------- -----------------------------------

V3 V~water_table~

Fluctuations in the water table as indicated to the depth of the
seasonal high water table. The water table of organic flat systems
undergo drawdowns due to evapotranspiration and drainage, and rises due
to precipitation. Drawdowns of the water table combine with pore space
to provide potential volume for water storage below the ground surface.

  ----------------------------------------------------------------- -----
  A. Hydrology has not been significantly altered by drainage       1.0
  structures                                                        

  B. Wetland hydrology has been modified by drainage structures but 0.5
  the site is not considered significantly altered (includes FW and 
  FWP)                                                              

  C. Wetland hydrology has been modified by drainage structures,    0.1
  and the site is considered to be significantly altered. This also 
  includes Prior Converted wetland (PC). Restoration is possible.   

  D. Evaluation area is such that restoration is not possible.      0.0
  ----------------------------------------------------------------- -----

[V4 V~avail_H2O~]{.underline}

Available Water Capacity (AWC) is the volume of water available to
plants. It is the amount of water held between field capacity and
wilting point, with corrections for salinity, fragments, and rooting
depth. AWC is based on an average of the top 40" of soil or to a
limiting layer.

  ------------------------------------------------------ ----------------
  A. Typic Subgroups Available Water Capacity is 0.4     1.0
  in./in.                                                

  B. Terric Subgroups Available Water Capacity is        0.5
  0.30-0.39 in./in.                                      

  C. Linmic Subgroups Soils compacted, or AWC 0.20-0.29  0.25
  in./in.                                                

  D. Shallow mucks Available Water Capacity is\<0.20     0.1
  in./in.                                                

  E. Soils replaced by substrate with negligible pore    0.0
  space (e.g. concrete, asphalt). Restoration is not     
  possible.                                              
  ------------------------------------------------------ ----------------

[V5 V~strata~]{.underline}

Mature forested wetlands are usually vertically stratified. Forest
organisms are primarily associated with a specific strata. Differences
in structure between sites likely represent differences in animal
composition between the sites as well. In fact, more spatially
stratified communities often contain more species.  

A. Four vegetative strata present (trees, shrubs, vines, and
herbaceous). 1.0

B. Three vegetative strata present. 0.75

C. Two vegetative strata present. 0.5

D. One perennial vegetative strata present. 0.25

E. Area converted to row crop agriculture; restoration is possible. 0.1

F. Area converted to row crop agriculture; restoration not possible. 0.0

[V6 V~canopy~]{.underline}

This is a measure of the continuity of the upper layers of the forest
canopy. It is assumed the more complete the canopy cover the more
efficient the wetland is at nutrient cycling regardless of the maturity
of the stand. Stands with canopy coverage of 80-100% provide optimal
habitat for forest wildlife.

A. Tree canopy cover \>80%. 1.0

B. Tree canopy cover 50-80%. 0.5

C. Tree canopy 10-50% 0.25

D. Site is not forested or has a tree canopy \<10% potential for
recovery 0.1

E. No tree canopy; no potential for recovery (site not suited for trees)
0.0

[V7 V~turnover~]{.underline}

Detrital stocks are represented by down and dead woody debris, and
organic debris on the forest floor. Standing stocks of detritus are
assumed to be proportional to annual turnover. Most of the annual
nutrient cycling occurs at the surface and subsurface levels, therefore,
organic debris found on the ground as coarse woody debris and as part of
the soil profile are indicative of the active biomass fraction and are
representative of annual detrital turnover in the system. An appropriate
number of sample plots will be taken to calculate the final score for
this variable. Indicators include:

-   Downed and dead woody debris

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-   Leaf litter layer

-   Snags

A. Three indicators are present. 1.0

B. Two indicators are present. 0.50

C. One indicator is present. 0.25

D. Area barren of woody debris potential for recovery. 0.1

E. Area barren of all elements; no potential for recovery. 0.0

[V8 V~basal\ area~]{.underline}

This is a measurement of the average tree basal area within the
evaluation area. Trees are defined as greater then 4 inches DBH. Basal
area is proportional to above ground biomass of trees and is a
dependable indication of forest maturity. In mineral flat forests, basal
area and stem density both increase in early succession. Thereafter,
tree density decreases, and, as the forest reaches maturity, the rate of
increase of basal area diminishes to steady-state conditions.

  ------------------------------------------------------- ---------------
  A. Basal area \>100 sq. ft.                             1.0

  B. Basal area 70 -100 sq. ft.                           0.75

  C. Basal area 40-70 sq. ft.; forested site              0.50

  D. Basal area \<40 sq. ft.; forested site \>300         0.25
  trees/acre                                              

  E. Restoration possible, e.g. PC, FW, etc.              0.1

  F. No trees present; restoration not possible.          0.0
  ------------------------------------------------------- ---------------

[V9 V~soil_OM~]{.underline}

This variable is defined as the organic matter (OM) content of the upper
51 inches of the soil profile.

A. Typic Subgroups, e.g. Houghton 1.0

B. Terric Subgroups, e.g. Palms, Adrian 0.5

C. Limnic Subgroups, e.g. Muskego 0.25

D. Shallow mucks, e.g. Antung 0.1

E. Restoration is not possible due to site constraints. 0.0

[V10 V~comp~]{.underline}

This variable is defined using 1/10th acre plots for the tree strata to
determine the dominant tree species. Native tree species are present to
fully stock the site, e.g. the site would be considered as forested.
(also includes seedlings). This variable we be calculated using an
average for the site if applicable. The 50/20 rule will be used.

An appropriate number of sample plots will be taken to calculate the
final score for this variable.

A ≥4 species are present. 1.0

B. 3 species are present. 0.75

C. 2 species are present, res. 0.50

D. 1 species is present. 0.25

E. Site is not fully stocked with trees e.g. cropland, pasture etc. 0.1

F. Restoration is not possible. 0.0

[V11 V~maturity~]{.underline}

Standing and mature or dying trees provide nesting habitat for a variety
of animal species, including invertebrates, birds, reptiles, amphibians,
and mammals. Mature trees provide a significant amount of food for
wildlife species as well as leaf/woody debris for the nutrient cycle. An
appropriate number of sample plots will be taken to calculate the final
score for this variable.

A. [\>]{.underline}5 trees/ac. [\>]{.underline}16 inches DBH 1.0

B. 2-4 trees/ac. [\>]{.underline}16 inches DBH [or,]{.underline} 0.75

[\>]{.underline}5 trees/ac. [\>]{.underline}12 inches DBH

C. \>30 trees/ac. \>6 inches DBH 0.5

D. \>300 stems/ac (including trees, shrubs, and seedlings) 0.25

E. No trees present; restoration possible, e.g. ag. land. 0.1

F. No trees present; restoration not possible. 0.0

[V12 V~snags~]{.underline}

This variable is defined as the density of standing dead trees (\>4
inches DBH and \>6 feet tall). Standing dead trees (snags) are a normal
component of forested wetlands. The density of standing dead trees
relates to the suitability of a site as wildlife habitat due to the
large number of species that forage on, and nest and den in snags. It
may also provide an insight into the hydrology of the site. More
standing dead trees than a typical site might show an increase in
ponding on the site.

A. \>5 snags/ac. 1.0

B. 2-5 snags/ac. 0.5

C. 1 snags/ac. 0.25

D. Ag. land restoration possible. 0.1

E. No snags present; restoration not possible. 0.0

[V13 V~migrate~]{.underline}

This variable considers that small woodlots (3-5 acres) are important as
migratory stop over sites for forest-interior bird species. Acreage for
this variable includes the wetland and contiguous woodland associated
with the wetland. Area calculations can be made directly from an NWI or
topographic map, or from aerial photos.

A. \>5 acre woodlot. 1.0 B. 3 - 5 acre woodlot. 0.5

C. 2 - 3 acre woodlot. 0.1

D. 2 \< acre woodlot. 0.0

[V14 V~contig~]{.underline}

Heterogeneity in distribution and abundance of organisms is inherent at
all scales in every natural ecosystem. Any measure of ecosystem
attributes must consider the appropriate scale and sample size in which
to measure those attributes in order to understand ecosystem processes.
Patchiness of vegetation (lack of contiguous cover types) affects the
types and abundance of trophic interactions, energy flow, and
competitive interactions of animals. These processes in turn affect
animal populations.

A. The wetland is part of a larger block (\>40 acres) of contiguous
upland and/or 1.0

wetland forest which is non-fragmented and has few non-natural breaks.

B. Wetland is part of a 30-40 acre block as above. 0.75

C. Wetland is part of a 20-30 acre block as above. 0.5

D. Wetland is part of a 10-20 acre block as above. 0.25

E. Wetland is part of a block \<10 acres, or is part of a highly
fragmented larger 0.1

block; restoration is possible. Include PC that and non wetlands.

F. Wetland is part of a block \<10 acres, or is part of a highly
fragmented larger 0.0

block: restoration is [not]{.underline} possible (Example: urban area).

[V15 V~connect~]{.underline}

This variable is defined as the distance from the wetland's perimeter to
other "suitable" habitat for wildlife. Many species of wildlife that are
common inhabitants of forested wetlands also may use other habitat such
as upland forests.

This variable is assessed by measuring the distance from the wetland to
other types of wetlands, to upland forest habitat, or to other
communities capable of providing habitat for at least some of the
species typically associated with forested wetlands. At least 20% of the
perimeter of the wetland being evaluated must meet the described
distance measurements. Minimize size of woods to be connected to is 3
acres.

A. A direct connection of continuous woody or shrubby cover ≥50' in
width is present. 1.0

Examples include hedge rows, fence rows, windbreaks, etc.

B. A direct connection of continuous woody or shrubby cover 50'\< in
width is present. 0.75

Examples include hedge rows, fence rows, windbreaks, etc.

C. A direct connection does not exist, but suitable habitat is \<1/4
mile from 0.50

the wetland perimeter..

D. A direct connection does not exist, but suitable habitat is 1/4-1/2
mile 0.25

from the wetland perimeter.

E. A direct connection does not exist, but suitable habitat is \>1/2 0.1

from the wetland perimeter. Include PC that and non wetlands.

F. Site cannot be restored, e.g. urban land etc. 0.0