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Changes in structure in semi-desert grasslands following restoration of fire.
Geiger, Erika*,1, McPherson, Guy1, 1 University of Arizona, Tucson, Arizona, USA
ABSTRACT- In an effort to recreate pristine semi-desert grasslands in the southwestern United States, land managers have touted restoration of fire as the most appropriate tool. Yet, fires often are implemented contrary to historic fire regimes and into vastly altered systems. In southwestern grasslands, Eragrostis lehmanniana, a nonnative perennial grass from southern Africa, is implicated as the cause for loss of native organisms. Currently, land managers use fire in controlling this nonnative species despite considerable evidence demonstrating the benefits of fire to E. lehmanniana. We designed a large-scale experiment in the semi-desert grasslands of southeastern Arizona to quantify changes in plant community structure following fire treatments (spring, summer, no fire) across a gradient of dominance by a nonnative grass. There was a slight change in the proportion of E. lehmanniana following fires (increase following spring fire, decrease following summer fire), but these differences faded within 1 year. Richness in these grasslands was consistently negatively correlated with proportion of E. lehmanniana biomass to total biomass regardless of year, season, community, or fire treatment. Additionally, richness appeared to be influenced more by year-to-year variability than by fire treatment. A decrease in total biomass was maintained for two fall seasons following fire, a response that varied by treatment season and year. Because of variability of responses across years, continued experimental research is needed before fires may be restored on a large scale.
Key words: nonnative, grasslands, fire, restoration