Effect of Fire on Bunchgrasses of the Sagebrush‐Grass Region in Southern Idaho

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Abstract
Four species of bunchgrass were experimentally burned in a portable combustion chamber to determine their resistance to fire as a function of season of burning (June, July, August), intensity of burn (200°F, 400°F), and plant size. Poa secunda was not affected by burning. Sitanion hystrix proved comparatively resistance to burning; it was damaged in July only. This seasonal response correlates with air temperature and relative humidity, which appear to influence the amount of applied heat required to cause damage. Of the species tested, Stipa comata appeared to be most susceptible to fire. The plants suffered high mortality in June, were extremely susceptible to damage from burning in July, but were relatively resistant to fire in August. The seasonal response of Stipa thurberiana was similar to that of Stipa comata, but damage was less severe. Season of burn was the primary determinant of the extent of damage to Stipa species during June and July, but size of plant became increasingly important in determining the effect of burning during the latter part of summer. The difference between maximum soil surface temperatures of 200°F and 400° was apparent only for small Stipa thurberiana plants burned in June.