PHYSIOLOGICAL CONTROL OF CHAMISE SHOOT GROWTH AFTER FIRE

Five controlled burns (ca. 2 ha each) were conducted in the Coast Range of northern California near Hopland, California, between November 18, 1975 and September 15, 1976 to determine the effect of shrub phenology on the sprouting response of chamise (Adenostoma fasciculatum H&A) following fire. The time of burn had little effect on the amount of shoot growth that occurred after fire, although the pattern of growth was altered. Shrubs burned on June 22 or August 2, 1976 grew continually until August 1977, while unburned shrubs or those burned at other times ceased seasonal growth during the first summer after fire. Neither the amount nor the pattern of shoot growth was influenced by the shrub water status before the fire occurred. The relationship between chamise shoot growth after fire, ¹⁴CO₂ fixation, xylem sap tension, and air temperature was also studied. The growth rate of regrowing shrubs was highly correlated with ¹⁴CO₂ fixation prior to the growth measurement. Water status (pre-dawn xylem sap tension) had a negative correlation with ¹⁴CO₂ fixation. The abundance of carbohydrate at the shoot apex is believed to influence the seasonal pattern and rate of chamise shoot growth following fire.