THE RELATIVE SENSITIVITY OF 2 BUNCHGRASS SPECIES TO FIRE

The response of two bunchgrass species, Festuca idahoensis and Agropyr on 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 doc umentation of the temperatures experienced in various regions of each plant during the fire and postfire cooling phases. A quantitative inde x of fire exposure, or severity, for each plant was obtained by integr ating 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 a ffect culm or biomass productivity. Culm production was initiated earl ier and more rapidly in Festuca than Agropyron, and within 60 days aft er fire exposure the total number of culms produced in Festuca was nea rly 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 pr oduction at a moderate fire severity, whereas high fire severity was r equired for this reduction in Festuca. Contrary to previous studies, F estuca thus appears less sensitive to fire injury than Agropyron.