Fire and Landscapes: Patterns and Processes

Fire has been a pervasive influence on the Sierra Nevadan landscape for millennia. Lake sediments containing charcoal and pollen indicate that fires have occurred for at least the past 13,000 years. Brunelle and Anderson (2003) found that charcoal accumulation varied with vegetation and temperature, increasing during warm periods dominated by oaks (Quercus spp.) and sagebrush (Artemisia tridentata) and decreasing during cool periods dominated by subalpine species, such as mountain hemlock (Tsuga mertensiana). They concluded that the lake sediment record was consistent with other long-term records of climate and vegetation in the Sierra Nevada and with records of fire and climate for the past 1,000 years as determined from tree-ring studies (Graumlich 1993). Although it is not possible to determine whether the frequency of lightning strikes varied during the period covered by the sediment record, the number of ignition sources was obviously sufficient to produce fires across the landscape.