Species richness, fire spread, and structural heterogeneity in tallgrass prairie
Document Type: Dissertation
Author(s): Devan A. McGranahan
Publication Year: 2011

Cataloging Information

  • fire
  • fire spread
  • grassland
  • grazing
  • Great Basin
  • heterogeneity
  • invasive grasses
  • Lolium arundinaceum
  • patch burn grazing
  • species richness
  • tall fescue
Record Maintained By:
Record Last Modified: November 12, 2015
FRAMES Record Number: 18097


This work addresses problems facing the ecological management of human-impacted grassland, specifically, the negative effects of invasive species and heavy grazing on biodiversity, and the barriers to restoring ecological processes, particularly fire, created by invasive species and heavy grazing. Of particular interest is the Eurasian cool-season grass, tall fescue (Lolium arundinaceum) and the effects of excessive livestock grazing, both historically and within the management timeframe. We focus on the Grand River Grasslands of Ringgold County, Iowa and Harrison County, Missouri. Grazing history and the abundance of a specific invasive species have contrasting effects on plant species richness in the GRG; we found no evidence that severe grazing reduced native species richness whereas native species richness declined with increasing abundance of tall fescue. Tall fescue invasion also reduced fire spread in fire behavior simulations. Grazing in the previous growing season reduced the total fuel load and increased the proportion of tall fescue in the fuelbed, exacerbating the negative effect of tall fescue invasion on fire spread. We attribute reduced fire spread to asynchrony in the growing seasons of the exotic, cool-season tall fescue and native, warm-season tallgrass prairie. Although spatially-heterogeneous fire has been shown to increase rangeland biodiversity, management for heterogeneity does not universally create contrast in the landscape. In our meta-analysis of five rangeland locations in Oklahoma and Iowa, management for heterogeneity created landscape-level heterogeneity in vegetation across a broad range of precipitation and plant community types, but management for heterogeneity did not universally create patch contrast. Stocking rate and invasive plant species are key regulators of heterogeneity-based management.

Online Link(s):
McGranahan, Devan A. 2011. Species richness, fire spread, and structural heterogeneity in tallgrass prairie. Doctor of Philosophy. Ames, IA: Iowa State University. 112 p.