Postfire Defoliation Response of Agropyron spicatum and Sitanion hystrix

Abstract

Prescribed fire is an important management tool to increase herbaceous productivity and maintain seral communities of Intermountain sagebrush grasslands. Currently, pastures treated with prescribed fire are rested from livestock grazing before burning to allow fine fuel accumulation, and rested a full year following burning to restore bunchgrass vigor. This study examined the post-fire defoliation response of Agropyron spicatum and Sitanion hystrix to three different defoliation treatments: an early season defoliation during the boot phenological stage, late season defoliation after seedset, and non-defoliation. Plant response to these defoliation timings was compared to determine the amount of non-use required to restore vigor to these species following fire. Mortality was low for late and non-defoliated plants of both species. Results indicate no differences between late season and non-defoliated plants for biomass production, basal area, or culm number for Agropyron. No differences in Sitanion culm number resulted between the late and non defoliated treatments. Sitanion biomass production differed between late and non-defoliated treatments at Emmett, but not at Craters of the Moon. Basal area and culm number of late and non-defoliated plants of both species increased as compared to the first post-burn season.