Response of Sitanion hystrix (Nutt.) J. G. to Prescribed Burning

Abstract

This study reports the response of Sitanion hystrix (Nutt.) J. G. to a midsummer controlled burn. Vegetative, reproductive and physiological attributes of control and burned plants were evaluated in the year following treatment using yield per unit of active crown area. Burned plants responded positively to fire for all parameters measured; (1) shoot biomass-.52 vs. .09 g.cm-2 (burn vs. control); (2) root biomass-.36 vs. .24 g cm-2; (3) inflorescence biomass-.26 vs. .02 g cm-2; (4) total shoot density-2.87 vs. 1.95 shoots. cm-2; (5) reproductive shoot density-2.14 vs. .28 shoots cm-2; and (6) total nonstructural carbohydrates of roots and crowns -6.66 vs. 5.29 g.cm-2. The results contradict previous reports which indicate a period of 1 to several years before preburn levels of annual production are regained. Direct effects of fire on quiescent bunchgrasses result from heat damage of crown meristematic tissue and subsequent reduction of active crown area. However, crown area of marked Sitanion plants was unchanged as a result of burning. Indirect effects of fire derive from alteration of the effective environment of treated plants. Growth of Sitanion appears to be related to fire-induced changes in the physical environment and competitive relations within the annual plant-dominated community. 'Squaw Butte Station, Eastern Oregon Agricultural Research Center, Burns, Oregon 97720. Eastern Oregon Agricultural Research Center is jointly operated by the Oregon Agricultural Experiment Station, Oregon State University and the Agricultural Research Service-U.S. Dep. Agric. Technical Paper No. 7003, Oregon Agricultural Experiment Station.