Name:
North American Boreal Flooded & Rich Swamp Forest Macrogroup
Reference:
NatureServe Biotics 2019
Description:
Boreal rich swamp and floodplain forests develop on wet soils where the interaction of climate and landscape results in permanent or semipermanent water tables at or near to the soil surface, but where water, nutrient and temperature regimes lie within the range required for tree establishment and growth. These wet forests are of two main types in boreal North America: (1) forests and woodlands that are strongly influenced by permanently high water tables where the flow rate, subsurface depth and alkaline chemistry of groundwater determine site moisture and nutrient characteristics, and (2) forests and woodlands on sites that do not have permanent water tables at or near the soil surface, but that may be seasonally flooded for short periods during the growing season; soils are freely drained such that anoxic conditions are quickly relieved after subsidence of floodwaters. The first case describes rich swamps. In the second case, flood ecosystems develop alongside waterbodies that periodically overflow their banks or where subsurface water tables are within the rooting zone for part of the growing season. These conditions do not usually cover extensive areas and typically occur on fine-textured mineral soils beside flood-prone rivers or lakes.<br /><br />Across all regions of the North American boreal, <i>Larix laricina</i> occurs with <i>Picea mariana</i> across all regions in treed wetlands that are moderately well-supplied with nutrients (intermediate to rich). In eastern Canada, <i>Abies balsamea</i> and <i>Betula papyrifera</i> also occur in intermediate wetlands; in western Canada, <i>Picea glauca</i> can be present. On nutrient-rich sites (rich swamps or flooded sites) with primarily mineral soils and where water tables draw down during the growing season, broad-leaved deciduous trees often dominate. <i>Populus balsamifera, Populus tremuloides, Betula papyrifera</i>, and <i>Picea glauca</i> are common across all regions. In Alberta, Saskatchewan and Manitoba, <i>Acer negundo</i> may also be an important constituent. East of the Manitoba-Ontario border, <i>Fraxinus nigra, Thuja occidentalis</i>, and <i>Abies balsamea</i> are prevalent. In Alaska, <i>Populus balsamifera ssp. balsamifera</i> is the dominant deciduous tree in floodplains in the continental boreal region, while <i>Populus balsamifera ssp. trichocarpa</i> is dominant in the subboreal region. <i>Picea glauca</i> may be codominant in mid-seral stages and becomes dominant in late-seral stages. <i>Picea x lutzii</i> replaces <i>Picea glauca</i> in the transitional region between the subboreal and temperate biomes.<br /><br />The moss flora of rich swamps (rich wooded fens) is dominated by brown mosses (e.g., <i>Tomentypnum nitens, Aulacomnium palustre</i>). Rich swamps with standing and flowing water and higher nutrient status support <i>Salix</i> spp. and <i>Betula</i> spp. shrubs as well as a higher diversity of sedges (especially <i>Carex</i> spp.) and grasses (especially <i>Calamagrostis canadensis</i>). <i>Cornus sericea</i> and, especially in eastern Canada, <i>Alnus incana</i> are important shrub species on nutrient-rich sites. The understories of hardwood swamps on moist, rich sites are typically vigorous and species-rich because of high light levels beneath the transmissive canopies of these small-leaved broadleaf trees. In Alaska, <i>Alnus viridis ssp. sinuata</i> occurs more commonly in the subboreal, while <i>Alnus viridis ssp. fruticosa</i> is more common to the north in the continental boreal. <i>Alnus incana ssp. tenuifolia</i> occurs on poorly drained floodplain terraces in both boreal regions. <i>Salix alaxensis</i> is the most common willow across both the subboreal and boreal regions. Other common willows include <i>Salix pulchra</i> and <i>Salix barclayi</i> (subboreal only).
Accession Code:
urn:lsid:vegbank.org:commConcept:40632-{2A35EF1B-CB97-4A37-991E-33EF2C102523}
Plot-observations of this Community Concept:
0
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