MANITOBA'S ECOCLIMATIC REGIONS Geoffrey A.J. Scott 4 Although humans have an enor- matic provinces, and portions of 4 of etation zones and soil types. mous potential to modify natural the 10 Canadian ecoclimatic prov- It is the overall role of climate, ecosystems, many human activities inces — the Grassland, Boreal, however, that accounts for the are both stimulated and/or limited Subarctic, and Arctic — are found northwest-to-southeast orientation by constraints imposed by the eco- in Manitoba (Figure 4.1).3 Because of Manitoba's major ecoclimatic re- system or climate. Whereas much of of their large size and internal vari- gions and zonal vegetation and southern and west-central Mani- ation, these provinces are subdi- soils. Types of vegetation cover and toba has already been drastically vided into ecoclimatic regions, and the distribution of freely drained modified during the last century by 8 such regions are represented in soils correlate strongly with in- agriculture, grazing, forestry, and Manitoba. creasing moisture availability as urban development to the point As the definition implies, each precipitation increases from west to that its original natural-vegetation ecoclimatic region has its own char- east (Figure 4.4), and also with in- covers are hardly recognizable, acteristic combination of soil types, creasing effective precipitation as many other regions in the north and vegetation cover, and wildlife that one moves from south to north. northeast appear quite pristine. An makes it distinct from any other re- Wetlands, however, do not con- appreciation of the great variety gion. Ecoclimatic regions therefore form to this climatically determined presented by Manitoba's soils and include communities that can be de- zonal distribution of vegetation and biota is therefore valuable back- scribed by their potential natural- soils, because poor drainage rather ground for any discussion of human vegetation cover using traditional than climate is more important in de- activities in the province, and this is terms such as prairie, aspen park- termining their location. Because best gained by reviewing all major land, boreal forest, tundra, wet- wetlands cover 41 percent of Mani- natural ecosystems1 within Manito- lands, etc. (Figure 4.2). As might be toba, and because all five Canadian ba's ecoclimatic regions. expected, a comparison of Figures wetland classes (fens, bogs, marshes, Ecoclimatic regions are "broad 4.1 and 4.2 shows a marked similar- swamps, and open shallow water) are areas of the earth's surface charac- ity in major boundaries, reflecting encountered here, the following dis- terized by distinctive ecological re- the primary consideration given to cussion would be incomplete if their sponses to climate, as expressed by vegetation cover in delimiting ecocli- characteristics were omitted.4 It is vegetation and reflected in soils, matic regions. Likewise, a compari- also important to note that vegeta- wildlife and water."2 At a more gen- son of vegetation and soil distribu- tion zonation throughout the prov- Copyright @ 1996. University of Manitoba Press. All rights reserved. May not be reproduced in any form without permission from the publisher, except fair uses permitted under U.S. or applicable copyright law. eral level, ecoclimatic regions are tions (Figures 4.2 and 4.3) confirms ince has had but the short span of hierarchically grouped into ecocli- the strong relationship between veg- postglacial time in which to develop EBSCO : eBook Collection (EBSCOhost) - printed on 9/19/2018 2:38 PM via UNIVERSITY OF MANITOBA AN: 497392 ; Stadel, Christoph, Everitt, John C., Welsted, John E..; The Geography of Manitoba : Its Land and Its People Account: s5519424.main.ehost 44 THE GEOGRAPHY OF MANITOBA and stabilize, and that even this short period has been marked by climatic changes sufficient to move vegetation zone boundaries a hun- dred kilometres or more in just the last 3,500 years alone.5 THE TRANSITIONAL GRASSLAND ECOCLIMATIC REGION Most of southwestern Manitoba is part of the Transitional Grassland Ecoclimatic Region, a zone where moisture deficits are sufficiently large that woody species are gener- ally stressed and herbaceous (grass- land) species favoured. Some excep- tions include treed pothole/lake fringes and riverine gallery forests, where abundant ground water is found. In terms of traditional natu- ral-vegetation zonation, this region is called the prairie (Figure 4.2). Before agricultural settlement, prairie grassland was exceptionally well adapted to the stressful cli- mate, with its droughts, fires, strong winds, and herds of grazing and soil-compacting plains bison. (Official binomial names of plant and animal species are found in Ap- pendices 4.1 and 4.2, respectively). In addition, both the palatability of the herbaceous cover and a huge soil biota favoured rapid nutrient recycling with little litter buildup. The limited leaching potential of the subhumid prairie climate, com- bined with humification of the enor- mous annual production of fibrous rooting systems, has promoted both nutrient- and humus-rich topsoils over postglacial time — the classic Black Earths or Chernozems (Fig- 6 ure 4.5). These Black Chernozems Figure 4.1 Ecoclimatic Zonation in Manitoba (Source: Ecoregions Working Group, have been shown to be ideal for pro- Ecoclimatic Regions of Canada, First Approximation [Ottawa: Environment Canada, duction of cereals and oilseeds, two Ecoregions Working Group of the Canadian Committee on Ecological Land Classification groups of domesticated species well Service, Conservation and Protection, 1989]) adapted to drier and sunnier mid- latitude continental summer condi- making many communities suscep- and biotic conditions represented tions. Much of the recent history of tible to fire. As a result this region is throughout this prairie or Transi- this ecoclimatic region has there- associated with a long history of tional Grassland Ecoclimatic Re- fore been one of almost total prairie both human- and lightning-induced gion, it can be readily subdivided on conversion by the plough, or altera- burning, which has influenced the the basis of dominant vegetation tion to pasture (Chapter 15). dominant biota of the region as well cover into three major ecosystem Before the arrival of European as soil development. types: mixed-grass prairie, aspen agriculture, the herbaceous cover Perennial grasses are especially parkland, and tall-grass prairie. provided ideal habitat for many suited to spring or summer burn- species of wildlife. Inevitably such a ing, sprouting soon afterwards and Mixed-Grass Prairie subhumid climate was also condu- offering fresh browse for herbivores Manitoba's mixed-grass prairie has cive to the production of late sum- such as bison. Because of the many been greatly reduced in size during Copyright @ 1996. University of Manitoba Press. All rights reserved. May not be reproduced in any form without permission from the publisher, except fair uses permitted under U.S. or applicable copyright law. mer herbaceous cover die-back, different types of cover, habitats, the last century because of en- EBSCO : eBook Collection (EBSCOhost) - printed on 9/19/2018 2:38 PM via UNIVERSITY OF MANITOBA AN: 497392 ; Stadel, Christoph, Everitt, John C., Welsted, John E..; The Geography of Manitoba : Its Land and Its People Account: s5519424.main.ehost Manitoba's Ecoclimatic Regions 45 Table 4.1 Land Surface of Manitoba Covered by the Major Soil Orders/ Great Groups Soil Type% of Land Surface Black Chernozem 9.6 Dark Gray Chernozem 4.8 Gleysol 6.9 Regosol 1.4 Gray Luvisol 5.6 Organic Soils 17.5 Eutric Brunisol 13.2 Dystric Brunisol 8.5 Organic Cryosol 17.9 Turbic Cryosol 6.8 Rock 7.8 Total 100.0 Source: University of Manitoba, Faculty of Agriculture, Principles and Practices of Commercial Farming in Manitoba, 5th ed. (Winnipeg: Univer- sity of Manitoba, Faculty of Agricul- ture, 1977), 33. with its outward-creeping ground- level branches, are found on well- drained sandy soils. Woody stands with shrubs and often trees are found in protected depressions such as the Pembina Valley, around pot- holes or small lakes, along rivers, and on sandy deltaic deposits (Case Study 4.1 on page 56). In addition, some grassland patches, such as those scattered throughout Riding Mountain National Park, are domi- nated by fescue and Kentucky bluegrass. Black Chernozems are the domi- nant soil order throughout the re- gion, whereas Regosols (poorly de- veloped soils) are found in the Spruce Woods and along flood- plains, and some patches of Solo- Figure 4.2 Potential Natural Vegetation Zonation in Manitoba (Sources: For tundra and netzic soils (which provide low-qual- forest tundra, K.P, Timoney et al., "The High SubArctic Forest-Tundra of North Western ity agricultural land) are found Canada: Position, Width, and Vegetation Gradients in Relation to Climate," Arctic where sodium-rich parent material 45[1992]:l-9; for boreal forest and mixed-woods, J.S, Rowe, Forest Regions of Canada [Ottawa: Department of the Environment, Canadian Forestry Publication 1300,1972]; for is present. Where soil textures are boreal-prairie transition, S.C. Zoltai, The Southern Limit of Trees on the Canadian Prairies loamy and drainage adequate, Black [Edmonton: Northern Forest Research Centre, Information Report NOR-X-128, 1975]; and Chernozems have good Canada for parkland and prairie, G.C. Trottier, Conservation of Canadian Prairie Grasslands: a Land Inventory (CLI) ratings for agri- Landowner's Guide [Ottawa: Environment Canada, 1992]) culture. While only 9.6 percent of Manitoba's soils are Black Chern- croachment by aspen, and occupies thread (or spear) grass, northern ozems and another 4.8 percent are only a small portion in the south- wheat grass, June grass, and little Dark Gray Chernozems, these two west and many small remnant ar- bluestem, together with broadleaf Great Groups provide the over- eas within the aspen parkland. Of- herbs and sedges in moister loca- whelming majority of all agricul- ten termed the "mesic mixed-grass tions (Figure 4.6). tural soils throughout the province prairie" to differentiate it from the On drier sites, shorter grass spe- (Table 4.1).