Open Wetlands Key

This is a dichotomous key to open wetland natural communities

Dichotomous keys work by making one of two choices. Start at number 1, and determine which of the descriptions best suits what you are looking at. Then click on the link under the "go to" column to take you to the next choice, and ultimately to the natural community description.

Number Description Go To
1 Tidal wetlands 2
1 Non-tidal wetlands 6
2 Saltmarshes: vegetation varies, saltmeadow cordgrass and/or smooth cordgrass present and often a major component; dominants also may include black-grass, sedges, etc. 3
2 Brackish to freshwater marshes; saltmeadow cordgrass and/or smooth cordgrass not prominent 4
3 Saltmarshes with saltmeadow cordgrass and/or smooth cordgrass totaling >35% cover, or with black-grass >35% cover; most other species clearly less abundant (not including low-growing species like goosetongue that may be extensive beneath the graminoids) Spartina Saltmarsh
3 Saltmarsh cordgrass and/or black-grass are not strongly dominant, "canopy" vegetation more a mixture of graminoids and forbs; chair-maker's rush typically present, and may be dominant Mixed Graminoid - Forb Saltmarsh
4 Shrubs dominant Alder Floodplain
4 Herbaceous plants dominant 5
5 Brackish tidal setting; vegetation a mix of tall graminoids and rosette-forming forbs; freshwater cordgrass and/or wire rush usually present; obligate freshwater species such as cardinal flower, sweet flag, and pickerelweed absent Brackish Tidal Marsh
5 Freshwater, near the upstream end of the tidal reach; vegetation graminoid-dominated, with wild rice and/or softstem bulrush typical; some obligate freshwater plants such as pickerelweed, cardinal flower, and/or sweet flag present Freshwater Tidal Marsh
6 Submerged or floating-leaved aquatic vegetation; emergent plants, if present, are mostly those that die back below the water in autumn 7
6 Not as above; lakeshores, rivershores, bogs, fens, marshes that are not permanently underwater or, if so, are vegetated with emergent vegetation that remains through the winter 12
7 Plants with emergent leaves dominant 8
7 Plants with floating or submerged leaves dominant 10
8 Pickerelweed dominant among the emergent species Pickerelweed - Macrophyte Aquatic Bed
8 Graminoids dominant among emergent species 9
9 Bulrushes and/or bayonet rush dominant Bulrush Bed
9 Cattails dominant Cattail Marsh
10 Some plants indicative of higher pH waters present, e.g. tapegrass, common waterweed, water stargrass, white water crowfoot, Robbins' pondweed, alpine pondweed, Vasey's pondweed, and straight-leaved pondweed; water-shield, pipewort, water lobelia, and pickerelweed absent or virtually so Circumneutral - Alkaline Water Macrophyte Suite
10 Alkaline indicators absent; vegetation usually includes pipewort, water lobelia, pondweed species other than those listed above, and/or water-lilies 11
11 Vegetation mostly floating-leaved plants and/or submerged plants with aquatic stems floating in the water column; water-lilies and pondweeds typically dominant; depth varies Water-lily - Macrophyte Aquatic Bed
11 Vegetation dominated by submerged plants (flower stalks may protrude) with leaves mostly on the substrate, often in rosettes; pipewort and water lobelia characteristic; water depth usually <1 m Pipewort - Water Lobelia Aquatic Bed
12 Gently-sloping sandy or gravelly pondshores (usually of small ponds in outwash basins) of Southern Maine where natural water levels usually drop by late summer, exposing progressive bands of vegetation. From the upland edge, a band of shrubs is followed by three-way sedge, bayonet rush, and narrow-leaved goldenrod in the upper shore zone, then pipewort or other submerged aquatic species in the most flooded zone. Golden pert and meadow beauty are usually present as indicators (see couplet 22 for herbaceous lakeshore vegetation that is not in distinct bands) Three-way Sedge - Goldenrod Outwash Plain Pondshore
12 Vegetation not obviously banded around a central pond whose water level drops through the season 13
13 Sphagnum and dwarf shrub dominated vegetation forming a thin layer over sloping bedrock (sometimes talus); only in subalpine or extreme maritime zones; peat may not remain saturated through the summer (may not be true wetlands) 14
13 Basin wetlands, or vegetation along lakeshores or rivershores; widespread 15
14 Bog-like vegetation forming a "blanket" on slightly sloping bedrock at the immediate coast, from Washington County east Heath - Crowberry Maritime Slope Bog
14 Bog-like vegetation in subalpine setting, on steep slopes over bedrock or talus of mountain slopes (see couplet 24 for basin wetlands on summit plateaus) Heath - Lichen Subalpine Slope Bog
15 Vegetation of rivershores or lakeshores, with the substrate primarily mineral rather than organic; mostly in linear bands following the shoreline; may be flooded seasonally, but out of the water for most of growing season 16
15 Wetlands in basins or along broad drainages, with organic soils or with an organic layer over mineral substrate; vegetation often covering a large part of the substrate; saturated through all or most of the year 24
16 On rivershores 17
16 On lakeshores or pondshores 23
17 Shrubs, mostly >1 m tall, predominate 18
17 Shrubs <1 m tall, or mixture of shrubs and herbaceous plants, predominate 19
18 Alder is dominant or co-dominant; virgin's bower is present Alder Floodplain
18 Dogwood and willows predominate Dogwood - Willow Shoreline Thicket
19 Mixed shrub-herb vegetation on sloping eroding river shores where substrate is constantly saturated by groundwater seepage; calciphilic fen species present, e.g., grass-of-Parnassus, Kalm's lobelia, sticky false asphodel; bryophyte layer at least locally well developed, with species other than Sphagnum dominant Circumneutral Riverside Seep
19 Vegetation of almost-flat rivershores or Lakeshore Sand/Cobble Beaches (see couplet 23), substrate gravelly to sandy and not constantly saturated to the surface by seepage; bryophytes sparse or absent 20
20 Tall graminoids and forbs dominant, forming a dense meadow; shrubs, if present, are rarely taller than the herbs; bluejoint, spotted joe-pye weed, and flat-topped white aster characteristic Bluejoint Meadow
20 Vegetation more sparse and not dominated by bluejoint 21
21 Beach heather a locally prominent dwarf shrub; islands of gray birch usually present; little bluestem one of the more common graminoids; documented in Maine only from Saco River drainage Hudsonia River Beach
21 Beach heather and little bluestem are absent or incidental 22
22 Sand cherry and roses the dominant dwarf shrubs, Laurentian/Cordilleran plants such as Huron tansy, alpine sweet broom, and alpine milk-vetch often present; in Maine documented only on far northern rivers Sand Cherry - Tufted Hairgrass River Beach
22 Tufted hairgrass, twisted sedge, or other forbs and graminoids are dominant; statewide Twisted Sedge Cobble Rivershore
23 Sparse vegetation on lakeshore cobble or sand beaches; silverweed typical, beach heather, or golden heather may be present Lakeshore Sand/Cobble Beach
23 Patchy or sparse vegetation on subalpine gravelly pondshores Mountain Alder - Bush-honeysuckle Subalpine Meadow
24 Bogs and fens: substrate is accumulated peat (undecayed to partially decayed), usually >0.5 m deep and with extensive Sphagnum on the surface, sometimes floating over water; constantly saturated 25
24 Marshes: substrate is mineral soil, often with a surface layer of well-decomposed organic matter (peat, typically sedge-derived, may be >0.5 m thick but is generally less); Sphagnum may be present but does not form an extensive deposit; some remain saturated, but many dry out for at least part of the growing season 37
25 Alpine or subalpine basin peatlands, near or above treeline Cotton-grass - Heath Alpine Bog
25 Lower elevation wetlands 26
26 Bryophyte-dominated, often in raised peatlands; substrate wet and unstable; vascular plants usually <25% cover and limited to low-growing species e.g. cranberries, horned bladderwort, and white beak-rush; very dwarfed leatherleaf or other ericads may be present Bog Moss Lawn
26 Shrub and/or herb cover more extensive; vegetation not primarily bryophytes 27
27 Shrub cover (including dwarf shrubs) exceeds graminoid cover 28
27 Graminoid cover equals or exceeds shrub cover, including dwarf shrubs 33
28 Vegetation dominated by tall shrubs (mostly >1.5 m); mountain holly, alder, and wild calla characteristic; standing water usually present among hummocks of Sphagnum; in peatlands often at the upland/peatland interface Mountain Holly - Alder Woodland Fen
28 Vegetation dominated by herbs or shrubs mostly under 1m tall, typically including abundant ericads; mountain holly and alder may be present but are not dominant 29
29 Shrubby cinquefoil a prominent shrub, and other circumneutral indicators present, e.g. livid sedge, grass-of-Parnassus, and/or Kalm's lobelia Shrubby Cinquefoil - Sedge Circumneutral Fen
29 Shrubby cinquefoil absent (or scarce) and other circumneutral indicators lacking 30
30 Shrubs relatively tall (often >1 m) with sweetgale, hardhack, and/or meadowsweet prominent; leatherleaf often present but other ericads not abundant; typically in standing shallow water without a continuous Sphagnum carpet Sweetgale Mixed Shrub Fen
30 Vegetation dominated by ericads (though sweetgale often present), usually well under 1 m tall; bogs and fens on well developed Sphagnum carpets 31
31 Low bog vegetation with dwarf huckleberry locally dominant (often patchy), >20% cover; black crowberry and/or deer-hair sedge also present though not necessarily at high cover; graminoid cover may be relatively high (often >25%); coastal (up to 15 miles or so inland) Huckleberry - Crowberry Bog
31 Other shrubs dominant, or if dwarf huckleberry dominant then neither black crowberry nor deer-hair sedge present; both coastal and inland 32
32 Weakly minerotrophic fen conditions (vegetation mostly in contact with the water table), with leatherleaf (or a combination of leatherleaf with bog rosemary and/or sweetgale) the dominant shrub; other shrubs and sedges mixed in; graminoid cover variable Leatherleaf Boggy Fen
32 Ombrotrophic bog conditions (vegetation mostly raised above the water table), with sheep laurel, Labrador tea, and/or rhodora together more abundant than leatherleaf and sweetgale; graminoid cover rarely exceeds 15% Sheep Laurel Dwarf Shrub Bog
33 Sedge-dominated lawns, deer-hair sedge and/or coast sedge characteristic; centrally located on raised (ombrotrophic) plateau bogs within about ten miles of the coast, Hancock County east Deer-hair Sedge Bog Lawn
33 Fen (minerotrophic) setting, areas sometimes transitional to bogs, but not the central lawn of a coastal plateau bog 34
34 Fens with circumneutral indicators e.g. livid sedge, yellow sedge, grass-of-Parnassus, Kalm's lobelia, and/or shrubby cinquefoil, usually with more than one indicator species Shrubby Cinquefoil - Sedge Circumneutral Fen
34 Circumneutral indicator species absent or virtually so 35
35 Vegetation dominated by tall sedges: dominant species are slender sedge, beaked sedge, and/or lake bank sedge; or rarely tussock sedge or inflated sedge Mixed Tall Sedge Fen
35 Slender sedge, beaked sedge, lake bank sedge, and inflated sedge not the dominant sedges, vegetation mostly lower 36
36 Carpets of low sedges over very wet Sphagnum substrate, with mud sedge, podgrass and white beak-rush characteristic; dwarf or creeping shrubs may be mixed with the sedges but are sparse (<20% cover) Low Sedge - Buckbean Fen Lawn
36 Sedges mixed with dwarf shrubs, usually >20% shrub cover; white beak-rush often present, but mud sedge and podgrass not; dominant sedges include few-seeded sedge, coast sedge, Michaux's sedge white beak-rush, and/or narrow-leaved cotton-grass Sedge - Leatherleaf Fen Lawn
37 Tussock sedge is the dominant herbaceous species (>30% cover, and usually >50%); shrub cover usually <30%; standing water between hummocks for much of season Tussock Sedge Meadow
37 Herb component dominated by species other than tussock sedge 38
38 Shrub cover exceeds herb cover 39
38 Herb cover exceeds shrub cover 41
39 Mixture of herbs and shrubs; dominant shrubs are not alder, sweetgale, or ericads, but are more often buttonbush or bog willow Mixed Graminoid - Shrub Marsh
39 Alder, sweetgale, and/or ericads are the dominant shrubs 40
40 Alders strongly dominant, >20% cover; ericads absent or virtually so Alder Shrub Thicket
40 Sweetgale and/or heath shrubs dominant, alders clearly subordinate Sweetgale Mixed Shrub Fen
41 Bluejoint dominates herb component, >50% cover; shrubs <25% cover Bluejoint Meadow
41 Mixture of herbs and shrubs (herbs 25-95%, shrubs 0-70% cover), without dominance of tussock sedge, bluejoint, or alder Mixed Graminoid - Shrub Marsh


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