Taiga Plains Mid-Boreal Ecoregion
Overview
The Taiga Plains Mid-Boreal (MB) Ecoregion has the mildest climatic regime in the Taiga Plains. Extensive till and lacustrine plains, organic blankets and alluvial deposits are typical landforms. Mixed-wood and jack pine stands, large fens and bogs with discontinuous permafrost are characteristic vegetation and wetland types.
General Description
The Level III Taiga Plains MB Ecoregion occurs across the southern third of the Taiga Plains and includes 11 Level IV Ecoregions, part of Great Slave Lake, and the southern reaches of the Mackenzie River. Much of the area was covered by glacial Lake McConnell, and the present-day landscapes are shaped by glacio-lacustrine and till deposits that have been reworked in places by fluvial, eolian, and mass wasting processes. The cold boreal climates and wet conditions in low-lying poorly-drained areas retard organic matter decomposition, and peatlands of varying thickness occur over extensive areas as patterned and horizontal fens, treed bogs, and peat plateaus, the latter on permanently frozen organic soils. On better-drained upland sites, the interplay of parent materials and active processes such as fire and alluvial deposition results in a mix of deciduous, mixed-wood and coniferous forests.
Climate
The Taiga Plains MB Ecoregion is classified as having a Mid-Boreal climate (Ecoregions Working Group 1989) and enjoys the mildest conditions in the Northwest Territories. There are a few stations from which climate models (Agriculture and Agri-Food Canada 1997) have been developed. These models provide the following statistics. The mean annual temperature ranges from –2.0 to –5.5ºC. The mean temperature in January, the coldest month, ranges from –25.5 to –28ºC, and from 15.5 to 16.5ºC in July, the warmest month. Mean annual precipitation is between 310 and 410 mm, with the wettest period in June through August and the driest period in December through April; about 55 percent falls as rain and 45 percent as snow. The mean annual daily solar input (refer to Section 1.4.1 for further explanation) ranges between 10.0 and 11.0 mJ/m2/day, with low values of 0.5 to 1.5 mj/m2/day in December and highs of 21.5 to 22.0 mJ/m2/day in June.
Topography, geology, soils, and hydrology
Most of the Taiga Plains MB Ecoregion is level to gently undulating, but the lower elevation portions of three major hill systems– the Cameron Hills, the Trout Upland, and the Horn Plateau – are partly included. On the plains and lowlands, extensive lacustrine and till deposits are often blanketed by peatlands that have developed since glacial times. Fluvial deposits occur along the Liard, Slave and Mackenzie Rivers. Pronounced slopes of major hill systems are ecologically distinct because of aspect, hydrology and mass movements. Bedrock has a significant effect on landscapes and vegetation in places. Major watercourses include the Mackenzie, Liard, Slave and Hay Rivers; the main lakes are Great Slave, Buffalo, Kakisa and Tathlina Lakes.
Vegetation
Productive mixed-wood, deciduous and coniferous stands occur on imperfectly- to rapidly drained mineral soils and form large continuous forests particularly in areas where fluvial processes are dominant, such as the Slave, Mackenzie and Liard Rivers. Jack pine stands are common after fire on coarse-textured soils. Elsewhere, upland forests occur less extensively on undulating or sloping terrain where drainage and soil conditions support their development. On level landscapes, water tables are usually high and organic materials have developed to varying depths; fens with black spruce, larch, dwarf birch, sedges and mosses are widespread, and peat plateaus (complexes of open, stunted black spruce-lichen forest and wet sedge-moss dominated collapse scars) are common.
Ecoregions
The following are the smaller ecoregions within the Taiga Plains Mid-Boreal Ecoregion:
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South Mackenzie Plain MB Ecoregion
Liard Plain MB Ecoregion
Liard Upland MB Ecoregion
Trout Upland MB Ecoregion
Horn Slopes MB Ecoregion
Great Slave Lowland MB Ecoregion
Tathlina Plain MB Ecoregion
Cameron Slopes MB Ecoregion
Slave Upland MB Ecoregion
Slave Delta MB Ecoregion
Slave Lowland MB Ecoregion
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Click here for more information on the Taiga Plains Mid-Boreal Ecoregion and all of the ecoregions within it.
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Total area: 106,876 km2 (22% of Taiga Plains)
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