Map Unit Summary and Naming Conventions


The goal is to present a classification that can be used to indicate, or model wetland functions.  Wetland functions are valued by society, and society has recognized these values and has created legislation to guide development activity occurring on wetlands.  Wetland functions are diverse, and probably no single map-able classification can be constructed to adequately model all wetland functions.  We could construct a map showing salmon spawning habitat, or flood plains, or sandhill crane foraging areas, all wetland functions that we value, but each of these maps would look different, and contain overlapping areas.  Knowing that we are faced with the essentially impossible task of creating a wetland map that can perfectly predict function, we set out to do just that.

We do know that the three criteria used to indicate jurisdictional wetlands: soils, vegetation and hydrology, can be used to model wetland function.  Certain soils have a greater moisture holding capacity, thus reflect total groundwater storage, an important flood control function of wetlands, for example.  With this in mind, a classification using local landforms, which control hydrology, the primary wetland indicator, was constructed, incorporating summaries of plant and soils occurrences.

The classification names presented in this document are on three levels, with the mapping units at the center.  The broadest level is represented by ecosystems, which describe the common landforms present on the Kenai; the middle level consists of the mapping components, which represent the variation of wetlands found within ecosystems- primarily using water table depth (hydrology); the third level is made up of the typical plant communities that occur within the mapping components.  Ecosystems are subdivided into mapping components which contain typical plant communities.  The plant communities and mapping components are not exclusive: any plant community can potentially occur in any component, and components can (and usually do) contain more than one plant community.

In this project, mapping units are the finest-scale names assigned to wetland polygons.  Map unit names are made up of one or more map components, outlined below.  With a few exceptions, described below, any single map unit is made of components from within only one ecosystem.  A few map unit names are a combination of two ecosystem names.  These represent polygons, often at fuzzy borders between ecosystems, where both systems are present at a scale too fine to delineate.  Plant communities do not nest exclusively into ecosystems or map components; any plant community can potentially occur in any mapping component, or ecosystem.  Strong affinities exist, but many exceptions also.  The map components, and rules for creating map unit names from them, are summarized below.

Mapping Methods



Summary of Depression Ecosystem Map Components:

D1- Standing water.  Floating or emergent vegetation.

D2 - Water table at or near the surface.  Sedge and/or sweetgale dominated.  

D3 - Water table does not reach the surface.  Shrubs or bluejoint grass (Calamagrostis canadensis) dominant.

D4 - Redoximorphic features or deep peat the wetland indicator.  Woodland or forest.

Depression map component combinations used so far: D12, D13, D1-3, D14, D1-4, D21, D23, D24, D2-4, D32, D34, D42, D43

Summary of Discharge Slope Ecosystem Map Components:

SM - Black spruce (Picea mariana) dominated.

SL - Lutz spruce (Picea X lutzii) dominated.

SS - Willow (usually Barclay's, Salix barclayi) dominated.

SG - White spruce (Picea glauca) dominated.

SC - Bluejoint grass (Calamagrostis canadensis) dominated.

SA - Alder (usually thinleaf alder, Alnus incana ssp tenuifolia) dominated.

Discharge Slope Ecosystem Map Component combinations used so far: SAC, SAG, SAL, SAM, SAS, SCA, SCL, SCS, SGA, SGM, SGS, SLA, SLC, SLM, SLS, SMA, SMG, SML, SMS, SSA, SSC, SSL, SSM

Summary of Relict Glacial Drainageway Ecosystem Map Components:

DW1- Standing water.  Floating (rare) or emergent vegetation.

DW2- Water at or near the surface.  Sedges, buckbean (Menyanthes trifoliata) and/or sweetgale (Myrica gale) dominant.

DW3- Deeper water table: hummocky or tussocky micro-topography.  Variety of plants; usually with a shrubby component.

DW4- Water table variable.  Bluejoint (Calamagrostis canadensis) dominated (uncommon map unit).

DW5A- Deeper water table.  Peat or redoximorphic features the wetland indicators.  Forested.

DW5- Deeper water table.  Usually with a deep peat layer and well-developed sphagnum mat.  Not forested.

Drainageway Complex:

DWR- A complex, usually of DW2 and DW3 with either DW5A or DW5.  This is most often a wet forest (DW5A) with a sedge (DW2) and shrubby, hummocky (DW3) understory.

Drainageway Map Component combinations used so far: DW12, DW1-3, DW1-4, DW1-5, DW1-5A, DW21, DW23, DW24, DW2-4, DW25, DW2-5, DW25A, DW2-5A, DW31, DW32, DW34, DW35, DW3-5, DW35A, DW3-5A, DW42, DW43, DW45, DW45A, DW4-5A, DW52, DW53, DW54, DW55A, DW5A2, DW5A3, DW5A4, DW5A5, DW3T6

Summary of Headwater Fen Map Unit Summaries:

H1: A small lake in a headwater basin.

H2: Sedge dominated peatland in a headwater basin; water table at or very near the surface.

H3: Shrub or bluejoint dominated peatland in a headwater basin; deeper water table.

H4: Woodland/forested peatland in headwater basin.

Headwater Fen Ecosystem Map Component combinations used so far: H13, H1-3, H21, H23, H2-4, H32, H34, H43

Summary of Kettle Ecosystem Map Components:

K1- Standing water; often a lake.  Submerged, floating and emergent vegetation.

K2- Water table at or near the surface.  Sedge and/or sweetgale (Myrica gale) dominated.

K3- Water table not at the surface.  Usually shrub dominated.  Can contain ombrotrophic bogs.

K4- Deep peats or redoximorphic features near the surface in a mineral soil.  Woodland or forest.  Can include bogs.

Kettle Ecosystem Map Component combinations used so far: K12, K13, K1-3, K1-4, K21, K23, K24, K2-4, K31, K32, K34, K42, K43

Summary of Relict Glacial Lakebed Ecosystem Map Components:

LB1- Standing water.  Floating or emergent vegetation.

LB2- Water table at or near the surface.  Sedge and/or sweetgale (Myrica gale) dominated.

LB3- Sphagnum peat well-developed, though not necessarily fibric (undecomposed).  A variety of sphagnum - sedge and sphagnum - ericaceous shrub communities, with sphagnum cover continuous and vascular plant cover sparse.

LB4- Peat well-developed.  Shrubby strangs.

LB5- Water table variable.  Dominated by bluejoint (Calamagrostis canadensis) (uncommon map unit).

LB6- Deep peat.  Woodland or forest, if Lutz spruce then usually with field horsetail and dwarf birch, if black spruce, then with Labrador tea.

Lakebed Complex:

LBSF- More than two of the above units present in a pattern too fine grained to map separately.  Often shallow pools alternating with peaty ridges about 20-50 meters apart.

Map Component combinations used do far: LB12, LB1-3, LB14, LB1-4, LB1-5, LB21, LB23, LB24, LB2-4, LB25, LB2-5, LB26, LB2-6, LB31, LB32, LB34, LB36, LB3-6, LB41, LB42, LB43, LB45, LB46, LB4-6, LB54, LB56, LB62, LB63, LB64

Summary of Riparian Ecosystem Map units:

AMT- Abandoned meander terraces and channels.  Limited to a few reaches along the Kenai and Kasilof Rivers.

REl- Linear, low gradient, pool dominated, on glacial deposits.

REs- Sinuous, low gradient, pool dominated, on glacial deposits.

REb- Bank-full due to beaver dam, roads, logging debris or natural obstruction.  Low gradient, on glacial deposits.

REa- Stream surface not discernable on 1:25,000 B&W aerial photography.  Low gradient, pool dominated.  On glacial deposits.

RB- Higher gradient (>2%); riffle dominated.

RC- Floodplain developed.  Point bars.  Riffle/pool morphology.

RDA- Multiple low gradient, pool- dominated channels on glacial deposits.

Rt- Tidally influenced river or stream.  Usually too small to map but extends about a mile on larger streams, and several miles on the Kasilof and Kenai Rivers.

Late Snow Ecosystem Component:

LSP:  Late Snow Plateaus.  Mineral soil; micro-lows and micro-highs present; sometimes on a slope up to 10%, but usually little relief.  Shallow water table or redoximorphic features indicating the water table is seasonally near the surface.  Above 500 meters elevation.

Tidal Flat Ecosystem Components:

T0- Bare mud

T1- saltpannes.  Sparse, low glasswort (Salicornia maritima) and pearlwort (Sagina maxima).

T2- Mud with creeping alkaligrass (Puccinellia phryganodes). Vince and Snow's (1984) "Outer Mudflats zone 1".  Inundated 26-46 times per summer (mean=34).

T3- Bare ground with goosetongue (Plantago maritima) and seaside arrowgrass (Triglochin maritima).  Vince and Snow's (1984) "Inner Mudflats zone 5".  Inundated 6-13 times per summer (mean=8).

T4- Alkaligrass (Puccinellia nootkaensis and P. Hultenii) dominates, usually with a beachrye (Leymus mollis ssp. mollis) component.  Loosely follows Vince and Snow's (1984) "Outer Mudflats zone 2" which is inundated 10-20 times per summer (mean=15).

T5- Ramensk's sedge (Carex ramenskii) dominates with pools.  Mare's tail (Hippuris), spikerush (Eleocharis spp.), saltmarsh starwort (Stellaria humifusa) found in and around the pools.  Vince and Snow's (1984) "Outer Sedge Marsh zone 3".  Inundated 0-5 times per summer (mean=3).

T6-  Lyngbye's sedge (Carex lyngbyei) cover nearly continuous.  Vince and Snow's (1984) "Outer Inner Sedge Masrh zone 7".  Inundated 0-4 times per summer (mean=2).

T7-  Beachrye (Leymus mollis ssp. mollis) diverse plant community on storm berms.  Probably in the same position as Vince and Snow's (1984) "Riverbank Levee zone 6", which is innundated 0-2 times per summer (mean=1).  Vince and Snow did not include beachrye in their Susitna Flats plant zonation work, except to mention that it becomes more abundant above about 12 cm "relative altitude" ("...relative to about 10 m above mean low water of spring tides").

T8- Pacific silverweed, largeflower speargrass (Poa eminens) and sometimes circumpolar reedgrass (Calamagrostis deschampsioides) dominate.  A combination of Vince and Snow's (1984) "Riverbank Levee zone 6" and "Inner Mudflats zone 4".  Inundated 0-2 (mean=1), and 8-13 (mean - 11) times per summer, respectively.  On the Kenai, "Riverbank Levees" are typically dominated by beachrye (Leymus mollis ssp. mollis).

T9- Upper reaches of low gradient river mouths; dominated by manyflower sedge (Carex pluriflora).  Vince and Snow's (1984) "Inner sedge marsh zone 8".  Inundated 0-2 times per summer (mean=1).

TR- More than two non-consecutive units at a scale too small to map.  Typically formed where gradients are steep, such as along larger tidal guts or at estuaries of smaller streams.

Tcs- Barren sand, gravel, cobbles and some boulders, at the high storm line below bluffs.

Tidal Ecosystem Map Component combinations used so far: T04, T0-4, T05, T14, T1-4, T17, T23, T2-4, T29, T32, T34, T35, T3-5, T36, T37, T40, T41, T42, T43, T45, T46, T4-6, T51, T53, T54, T56, T5-7, T58, T64, T65, T67, T6-8, T69, T6DW3, T73, T74, T76, T78, T86, T87, T96, T98, T9K3, T9LB3, T9SA, T9SC


Components outside of Ecosystems:

WU- Wetland /Upland complex.  Greater than 25% cover of wetlands of any ecosystem at a scale too small to map, in a larger unit.

DISTURB- Wetlands with human generated disturbance sufficient to mask pre-disturbance character of entire polygon.

Download final shapefile (v3.  14.6Mb- In ArcView 9.x you'll need to point to the layer's data source, under 'properties', 'source' to view the full legend).  Metadata.  Includes Seward wetlands, complete Habitat Function fields and a full 283 element legend covering both Seward and the Lowlands.



 Introduction and Key to Plant Communities  

Introduction and Key to Ecosystems

    Kenai Hydric Soils    Map Unit Summary    Methods    Glossary


Contact: Mike Gracz
Kenai Watershed Forum 
PO Box 15301
Fritz Creek, AK  99603

05 May 2007 08:04