Wooded Wetlands Key

This is a dichotomous key to wooded 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 Peat-substrate wetlands dominated by conifers or, less commonly, red maple. The herb layer is dominated by typical bog plants such as leatherleaf, sheep laurel, or other heath plants, cotton-grasses, white beak-rush, or sedges. Peat moss usually occupies more than 25% of ground surface. Sites occur on peat substrates in basins (peat >30 cm deep, usually more), or rarely with thinner peat over mineral soil; not on slopes 2
1 Mineral-soil wetlands or floodplains dominated by hardwoods or, less commonly Atlantic White Cedar or red spruce. The herb layer is dominated by plants other than the bog species listed above. Peat moss may be present on ground surface but generally occupies <20% cover and rarely forms a peat deposit of more than 15 cm; in drainages or on gentle slopes 10
2 Red maple dominant in canopy, or co-dominant with larch (less commonly, spruce); occasionally, larch may be dominant and red maple far less abundant; canopy closure usually <50%, occasionally somewhat higher (to 65%) Red Maple Wooded Fen
2 Conifers other than larch dominant in canopy 3
3 Northern white cedar dominant in canopy 4
3 Other conifers dominant 5
4 Closed-canopy or nearly closed-canopy forests (almost always >60% canopy); heath shrubs <15% cover; usually in poorly drained basins where they may occupy most of the basin, rather than occurring as part of a larger peatland vegetation complex Northern White Cedar Swamp
4 Canopy more open (usually <50%); partially wooded fens that are part of a larger peatland vegetation complex; heath shrubs or other dwarf shrubs usually >15% cover Northern White Cedar Woodland Fen
5 Atlantic white cedar dominant or at least common 6
5 Atlantic white cedar absent (or very incidental) 7
6 Closed-canopy (or nearly so) forests, >60% tree cover; shrubs only patchily abundant in openings Atlantic White Cedar Swamp
6 More like an open bog, with trees patchy to sparse (<50% cover) and mostly stunted; abundant heath shrubs Atlantic White Cedar Bog
7 Pitch pine is the dominant tree (though black spruce may be present); southern and coastal Maine; uncommon Pitch Pine Bog
7 Black spruce is the dominant tree (may be stunted) 8
8 Organic soil (peat) is usually >50 cm deep; larch may be co-dominant; statewide and common. NOTE: Spruce - Fir - Cinnamon Fern Forests with an unusually deep peat layer may key here Spruce - Larch Wooded Bog
8 Mineral-soil flats in colder regions; substrate usually includes at least patches of poorly drained mineral soil, sometimes with a shallow peat layer (<30 cm deep) 9
9 Sites are primarily well-drained/xeric but often undulate with both wetland and upland patches; tree cover is typically <60% Spruce - Heath Barren
9 Sites are primarily poorly drained flats, tree cover is typically >60% Spruce - Fir - Cinnamon Fern Swamp
10 Conifers dominant (>50% of canopy) 11
10 Broad-leaved or mixed forests or shrublands with conifers <50% of the canopy 13
11 Atlantic white cedar dominant Atlantic White Cedar Swamp
11 Other conifers dominant 12
12 Red spruce or black spruce the most abundant conifer; red maple may be up to 40% cover Spruce - Fir - Cinnamon Fern Forest
12 Northern white cedar the most abundant conifer; red maple may be common here as well Cedar - Spruce Seepage Forest
13 Alder is the dominant cover; the shrub layer is usually well developed Alder Floodplain
13 Alder is absent or very minor, sometimes forming a fringe on the channel edge of some Silver Maple Floodplain Forests 14
14 Silver maple, red maple, or balsam poplar are the most abundant hardwoods, black gum absent; wetlands on alluvial flats bordering rivers or permanent streams 15
14 Other hardwoods (yellow birch, sugar maple, black gum, black or green ash, red oak) are more abundant than silver or red maple, or at least co-dominant; wetland setting various 18
15 Floodplain forests with silver maple dominant, and conifers absent or very sparse; usually along third order or larger streams/rivers Silver Maple Floodplain Forest
15 Red maple, American elm, or balsam poplar dominant in floodplain or basin adjacent to smaller stream 16
16 Balsam poplar dominant or co-dominant with American elm and ash. Floodplain species such as ostrich fern and virgin's bower present; northern Maine Balsam Poplar Floodplain Forest
16 Red maple, yellow birch, or hemlock dominant 17
17 Red maple dominant, silver maple and musclewood more or less absent; conifers may be >25% of canopy; in various settings, such as low basins and along small to medium-sized rivers and streams Red Maple - Sensitive Fern Swamp
17 High floodplain or terrace forests along medium to large rivers, most often with sugar maple or red oak dominant, sometimes with yellow birch or ash dominant; herb layer includes ostrich fern and a mixture of wetland and upland species; often found adjacent to but at slightly higher elevation than silver maple floodplain forests Hardwood River Terrace Forest
18 Hardwood or hemlock-hardwood swamps in small (typically <3 acre), often isolated basins; shrub layer of highbush blueberry or winterberry; red maple common, black gum often present. Sites are in southern and coastal Maine Hemlock - Hardwood Pocket Swamp
18 Swamps or seepage forests in broader basins; highbush blueberry, winterberry, and similar shrubs absent or very sparse; sites are statewide 19
19 Hardwood or hemlock-hardwood seepage forests on gentle slopes or discharge areas at level breaks in a slope; yellow birch, green ash, brown ash and/or white ash may also occur in the canopy and may be co-dominant with red maple; statewide Hardwood Seepage Forest
19 Basin wetlands on mineral soils or shallow peat; black ash is dominant or co-dominant with northern white cedar and red maple; more common in northern and eastern Maine Black Ash Swamp


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