Geologic grazing refuges and grassland diversity: A shortgrass steppe study
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Authors: D. G. Milchunas, and I. Noy-Meir
Date: 2004
Journal: Rangeland Ecology & Management
Volume: 57
Number: 2
Pages: 141-147
Summary of Methods: In the shortgrass steppe of Colorado, authors made comparisons of vegetation and species composition between grazed sites and geologic refuge sites, that were located in ravines and not exposed to livestock grazing. Exclosure experiments revealed that grazing was the major factor influencing differences in vegetation between the two sites. Little bluestem (Schizachyrium scoparium) plants in exclosures tended to be more similar to refuge site plants and had greater height, total tillers, and flowering tillers than grazed plants. Species richness was similar between the two sites but grazed areas were dominated by shortgrass steppe species while refuge areas had greater species diversity and were composed of a mixture of tall stature species, forbs, and shrubs. The refuge site used in this study tended to be more tall species dominated and even light grazing tended to shift the species composition from this vegetation type to the vegetation found in heavily grazed shortgrass steppe suggesting that this plant community is uncommon and will not likely become common in this historically grazed area.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: refugia, relict, herbivory, rare species, livestock grazing, rock bluffs and outcrops, drought
Annotation: Grazing in the area was relatively light compared to much of the shortgrass steppe of the Pawnee National Grassland; removal of standing biomass at the end of the grazing season in mid-October was visually estimated at about 30-35%. Five sites of ravine-isolated refuges were located that had steep enough walls to prevent access by livestock, but not to deer or small mammals, and that had adjacent grazed sites. In October 1997, cages were constructed for use as temporary exclosure cages in grazed sites. Plant measurements were made in late July of 1998, 1999, and 2000.
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