Interaction of Disturbances in Tallgrass Prairie: A Field Experiment

Abstract

A field study was conducted to address the roles of fire, cattle grazing, and the interaction of these two disturbances on plant species abundance and community structure in a tallgrass prairie. In 1985 and 1986, species composition was sampled in three replicates of the following grassland treatments: ungrazed + unburned (undisturbed), grazed + unburned, ungrazed + burned, and grazed + burned. Cover of the matrix—forming species Andropogon gerardii was significantly greater, while cover of the nonmatrix species Bromus tectorum was significantly lower, on the burned treatments than on the unburned treatments. The number and cover of annuals were significantly higher on the grazed treatments than on the ungrazed treatments. Species richness increased with increasing disturbance intensity. Diversity, however, was lowest on the ungrazed + burned treatment and highest on the grazed + burned treatment. Burning significantly reduced species diversity on ungrazed treatments, and grazing significantly increased diversity on the burned treatment. This study documented the dissimilar effects of different natural disturbances on grassland species, growth form characteristics, and community structure. In addition, the results emphasize the important role of interaction among disturbances on plant community structure in grasslands.