Relationships of Vegetation and Environment in Buffalo Wallows

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Abstract
Active and presently inactive buffalo [Bison bison] wallows in central and southwestern Oklahoma [USA] were examined to determine the distribution and seasonal variation of herbaceous species in relation to environmental factors. Species cover values and soil data were collected from 6 areas along a transect which spanned the long axis of each wallow and included adjacent prairie at each end. Vegetation composition inside both active and inactive wallows was consistently different from that outside wallows. In each case, these vegetational differences corresponded to differences in soil texture, soil moisture, available P and pH along the topographic gradient from wallow bottom to prairie. An ordination of sample from May, July and Aug. revealed seasonal differences in the vegetation of areas inside and outside active and inactive wallows. Vegetation inside inactive wallows, though largely characterized by mesic species, displayed a seasonal sequence similar to that outside these wallows. These changes were due to a seasonal shift from cool-season species in May to warm-season species in Aug. Seasonal patterns inside active wallows were related to the intensity and frequency of disturbance by ungulates. Where disturbance was minimal, Eleocharis spp. remained dominant throughout the season. Vegetation changes resulted from the seasonal fluctuation of minor species. In highly disturbed wallows, cover of Eleocharis spp. and other species associated with inundated conditions in May declined and that of grasses increased with time.