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Wooded Islands in a Sea of Prairie

Habitats

The Region of North Dakota lying generally west of the Missouri River shows biogeographic affinities with western habitats more than any other section of North Dakota. Grasslands here have been described as xeric mixed-grass prairie (Whitman 1962). Dominant plants of this prairie type include Western Wheatgrass (Agropyron smithii), Needle-and-thread (Stipa comata), Blue Grama (Bouteloua gracilis), Little Bluestem (Andropogon scoparius), Needleleaf Sedge (Carex stenophyla), and Threadleaf Sedge (Carex filifolia) (Stewart 1975). Livestock grazing (Fig. 3) is a common land use in this region and the intensity of grazing ranges from none to very heavy. Dryland farming is the predominant land use across much of western North Dakota. Within my study area, the principal agricultural land-uses are grazing, wheat farming, and haying.

Figure 3. Livestock grazing causes serious reductions in plant community diversity and the structural types of vegetation available for wildlife and virtually eliminates all natural reproduction of the vegetation.

Vegetation of the wooded draws varies considerably, and appeared to be related to the slope, aspect, and location of individual draws. The predominant tree species in most draws were Green Ash (Fraxinus pennsylvanica) and American Elm (Ulmus americana). General observations suggested that Boxelder (Acer negundo) was most prevalent on generally flat slopes, such as along river floodplains. As slope increased, the frequency of Boxelder decreased.

The general vegetation pattern at the upper ends of most wooded draws consisted of many small trees, high shrub densities, low canopy cover, and high ground cover. The lower ends were characterized by few large trees, few shrubs, high canopy cover, and lower ground cover. Grazing intensity appeared to have a pronounced affect on the understory vegetation to the draws (Fig. 4).

Figure 4. High structural complexity of the understory vegetation is maintained under light grazing by livestock.

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