Abstract The response of two bunchgrass species, Festuca idahoensis and Agropyron spicatum, to fire was examined under three levels of fire severity. The fire treatment was applied with an instrument system that allowed precise control over the intensity and duration of fire, and full documentation of the temperatures experienced in various regions of each plant during the fire and postfire cooling phases. A quantitative index of fire exposure, or severity, for each plant was obtained by integrating the temperature curve for the meristematic crown region over the fire and postfire cooling periods. No significant plant mortality was observed at any fire severity level. Although tissue damage in newly initiated culms was observed for Festuca, this did not significantly affect culm or biomass productivity. Culm production was initiated earlier and more rapidly in Festuca than Agropyron, and within 60 days after fire exposure the total number of culms produced in Festuca was nearly that of unburned plants. Aboveground biomass for both species was significantly less than that of unburned plants at the end of this 60-day period. Agropyron exhibited significantly less culm and biomass production at a moderate fire severity, whereas high fire severity was required for this reduction in Festuca. Contrary to previous studies, Festuca thus appears less sensitive to fire injury than Agropyron.

This research was funded by a grant form the Seed Grant Program, University of Idaho Research Council. Additional support was provided by the Idaho Forest, Wildlife and Range Experiment Station (Contribution no. 769).