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138 Chapter 12 The Big Picture Introduction Now that we have considered in detail the conifers and the ecosystems they create, it is time to see how this can be summarized by mapping the geographic extent of the ecosystems, and coincidentally the areas of dominance of one or more identifying conifer species. The result is a mosaic of “regions.” As ecologists well know, when you try to define boundaries between ecosystems, either in words or graphically on a map, a large number of rather subjective choices have to be made. Usually, there are no clear, natural boundaries, and the ones drawn on a map are unavoidably arbitrary. Maps are useful, but it pays to be aware of their limitations. Forest Regions A map of the forest regions is a necessity for any traveling naturalist faced with these questions: What are the predominant trees hereabouts, and why? The map in figure 12.1, and the tree lists that follow, are about as compact a way of presenting the information as is attainable. The letters used to label the regions are as follows: “T” and “B” represent the taiga and the boreal forest, respectively (some mappers combine them, treating the taiga as part of the boreal forest). “R” is the Pacific coast rain forest. “M” is the mountainous western region; it will be divided into subregions in the account below because it has three dissimilar the big picture 139 subregions too small to differentiate on a map of this scale. “G” and “A” represent the Great Lakes and St. Lawrence region and the Acadian region , respectively. “P” represents areas too dry for conifers. It supports prairie grasslands with a northern strip of trembling aspen and balsam poplar forest. Note that the boundaries of the zones are shown as stippled bands in the map, to emphasize that they are mostly broad and indefinite on the ground. Even as shown here, some are not fuzzy enough: where there is no abrupt change in climate and topography, an abrupt boundary is obviously inappropriate. Below are species lists of the principal conifers in the regions. For compactness some lists relate to pairs of regions, with species found in only one member of the pair differentiated with asterisks. The dominant trees in an area (those both large and abundant) are shown in capital letters. Two species (balsam fir and grand fir) are underlined to show that they grow only near the southern boundary of the region concerned. The subdivision of region M is as follows: “Ms” is land at high elevations on the several mountain ranges—the Rockies, Purcells, Selkirks, and Monashees on the east and, separated from them by a gap, the Coast Range and the Cascades on the west. “Mm” is the dry plateau country Figure 12.1. Map of the forest regions in the once-glaciated area. The regions, labeled by letters, are defined and briefly described in the text. (Map based on one in Trees of the Northern United States and Canada, by J. L. Farrar [Markham, Ontario: Fitzhenry and Whiteside, 1995].) 140 the world of northern evergreens between the two sets of mountain ranges, in the rain shadow of the coastal mountains; locally it’s called “the dry interior.” “Mc” is the so-called Columbian subregion or, more descriptively, the interior rain forest. It is on the lower slopes of the eastern mountains, far enough from the coastal mountains to escape their rain shadow effect. Now for the lists: REGIONS B AND T. (An asterisk marks trees never present in the tundra.) tamarack, white spruce, black spruce, balsam fir,* jack pine* REGIONS G AND A. eastern white pine, red pine, balsam fir, red spruce, white spruce, eastern hemlock, tamarack, jack pine, pitch pine, white spruce, black spruce, eastern juniper REGIONS R AND Mc. (An asterisk marks species only in the Pacific rain forest.) western redcedar, sitka spruce,* douglas-fir, western hemlock, western white pine, lodgepole pine, shore pine,* amabilis fir,* grand fir, mountain hemlock, western yew, Nootka-cypress, Rocky Mountain juniper REGION Ms. (An asterisk marks species only in the Rocky Mountains .) lodgepole pine, subalpine fir, engelmann spruce, douglasfir , whitebark pine, limber pine,* western larch, subalpine larch,* Rocky Mountain juniper REGION Mm. ponderosa pine, lodgepole pine, Douglas-fir In all the regions except the Great Lakes, the St. Lawrence, and the Acadian , conifers dominate. The forests of the latter two regions vary between coniferous and mixed (that is, with various broadleafs as well as conifers). Even a fuzzy map exaggerates the distinctness...


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