Taiga Shield Mid-Boreal Ecoregion
Overview
The Taiga Shield Mid-Boreal (MB) Ecoregion in the extreme southwest corner of the Northwest Territories Taiga Shield has a relatively warm climate, reflected by vigorous mixed-wood, deciduous and coniferous forests and extensive wetlands within a complex of low bedrock exposures and lacustrine or alluvial deposits.
General Description
The Level III Taiga Shield MB Ecoregion occupies a small area in the extreme southwest of the Northwest Territories Taiga Shield, and includes one Level IV ecoregion. It occupies the westernmost part of a former bay of Glacial Lake McConnell, which has over time partially filled with fine-textured lacustrine and alluvial materials. Exposed Precambrian Shield bedrock is characteristic of this Ecoregion and differentiates it from the climatically and ecologically similar Level IV Slave Lowland MB Ecoregion of the Taiga Plains to the west.
Climate
The Taiga Shield MB Ecoregion is classified as having a Mid-Boreal climate (Ecoregions Working Group 1989, Bradley et al. 1982). Fort Smith is the only station close to the Taiga Shield, and climate models developed by Agriculture and Agri-Food Canada (1997) for the area that includes the Ecoregion provide the following statistics. The mean annual temperature is –3.5ºC. The mean temperature in January, the coldest month, is –22ºC, and the mean temperature is 16ºC in July, the warmest month. Mean annual precipitation is between 330 and 360 mm, with the wettest period in May through October; about 60 percent falls as rain and 40 percent as snow. The mean annual daily solar input (refer to Section 1.4.1 for further explanation) lies between 10 and 11 mJ/m2/day, with low values of 1 to 1.2 mJ/m2/day in December and highs of between 21 and 22 mJ/m2/day in June.
Topography, Geology, Soils, and Hydrology
Rolling bedrock plains with small pockets of lacustrine sediments in low areas are the dominant landform in the northern half. Towards the south, bedrock exposures become lower and more widely separated, and near Fort Smith they are only present as scattered islands on a level lacustrine and fluvial plain. Peatlands cover nearly a third of the Taiga Shield MB Ecoregion, in sharp contrast to other Level III ecoregions within the Taiga Shield that average about five percent.
Vegetation
Productive mixed-wood, deciduous and coniferous stands occur on imperfectly- to well-drained lacustrine and fluvial deposits and are most extensive in the southern half of the Ecoregion. Jack pine and black spruce grow as scattered individuals or in small stands on shallow soils over bedrock, along bedrock fractures or on outwash sands. High water tables in the southern half support extensive wetland development. Appendix 2 summarizes the major plant community types.
Ecoregions
The following is the smaller ecoregions within the Taiga Shield Mid-Boreal Ecoregion:
Click here for more information on the Taiga Shield Mid-Boreal Ecoregion and the ecoregion within it.
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Total area: 6,639 km2 (2% of Taiga Shield).
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