Effects of competition on the postfire recovery of 2 bunchgrass species

Abstract

The effect of competition on the postfire recovery of Festuca idahoensis Elmer and Agropyron spicatum (Pursh) Scrib &Smith, was examined under natural conditions. Thirty plants of each species were exposed to fire applied with a portable instrument system that allowed precise control of fire temperature and duration, so that all plants received statistically similar fire severity levels inside the meristematic crown region. Treated plants were subjected to different levels of competition by periodically removing all or part of the aerial biomass around a monitored bunchgrass plant. Soil water potential, soil temperatures, and plant productivity were determined at monthly intervals during the growing season for the different competition treatments. No significant mortality due to fire was observed for plants of either species. Although Festuca did show meristematic tissue damage after fire, regrowth that occurred within 15 days after fire was more rapid than for Agropyron. Only Agropyron plants without competition reached prefire productivity levels. Soil water potential was significantly more negative in plots with competition. Temperatures in the upper 10-cm of the soil profile were significantly higher in plots without competition. Competition reduced root production and also restricted aboveground productivity by approximately 70% for Agropyron and 115% for Festuca. The capacity of these species to survive fire appears to be related more to the micro-environmental conditions created following fire and to their capacity to compete for available soil water, than to the direct effects of fire on plant tissues.