Effects of Patchburn Grazing on Vegetative Composition of Tallgrass Prairie Remnants in Missouri

Abstract

Patch-burn grazing is a grassland management approach that recouples the processes of fire and grazing altering animal distribution and creating structural heterogeneity for the benefit of flora and fauna biodiversity. Our objective was to investigate the effects of patch-burn grazing on plant species composition in tallgrass prairie remnants on conservation lands in Missouri. Each grazed unit consisted of three patches with each patch approximately one-third the size of the grazed unit. We burned a different patch annually and stocked the entire unit at a moderate rate of 0.45 AUM/ha with yearling stocker steers. We established paired plots of treatment (grazed) and control (grazing excluded) and sampled vegetative composition during a 3-yr graze-burn cycle and a fourth year of no treatments. Species richness, diversity, and floristic quality of exclosures were compared between plots using the Shannon, Simpson, and Floristic Quality indices. Our results indicated a year × treatment interaction. Specifically, species richness and floristic quality were significantly reduced in grazed plots during the first growing season post-burn (P < 0.05). However, after the first growing season post-burning and focal grazing, grazed plots no longer differed in diversity or floristic quality from ungrazed plots. Species richness remained elevated in grazed plots beyond the first growing season after burning and focal grazing. Species diversity showed no significant change in grazed plots throughout the study (P < 0.05) but results indicated a similar trend, declining during the first growing season post-burn followed by a spike the second year and recovery in subsequent years. More research is necessary to understand effects of long-term implementation of patch-burn grazing and on individual species. Despite the results of a companion study on horizontal structure, our results suggest that after one year of intense grazing following fire, any changes in vegetative composition were minor to nonexistent after three years of patch-burn grazing and one year of rest.