Rough fescue (Festuca campestris Rydb.) response to heat injury

Abstract

Rough fescue (Festuca campestris Rydb.) is an ecologically and economically important native plant species within grasslands of southwest Alberta. This is also a region where wildfires have become prevalent over the last decade. While the risk of long-term damage from fire may be determined by the susceptibility of rough fescue to heat injury, understanding the additive stress imposed by defoliation may assist in the development of grazing strategies facilitating rangeland recovery. Three laboratory studies were conducted to assess rough fescue sensitivity to heat stress, including the added impact of subsequent defoliation. Results indicated that fescue tillers were capable of withstanding temperatures of 60°C, but only for short periods (e.g., 16 s or less). At lower temperatures, a distinct interaction between exposure time and temperature was evident, with shorter times at greater temperatures causing similar reductions in growth as long exposure times at low temperatures. Decreased plant vigour, as evidenced by lower tiller numbers, resulted from defoliation coinciding with active regrowth, reinforcing the notion that rough fescue is sensitive to defoliation following heat stress. The greatest detrimental impact occurred with relatively longer periods of deferment (8 weeks) until defoliation following exposure to heat treatment. These results have implications for the recovery and conservation of burned rough fescue rangeland. Key words: Defoliation, Festuca campestris Rydb., heat stress, mortality, tillers, water bath