Managing natural wildfires in Sierra Nevada wilderness areas.

Past policies of excluding all wildfires from forests throughout the US are giving way to new strategies that incorporate naturally ignited fires into forest and fire management. In this paper, we evaluate the effects of long-standing natural fire programs (now referred to as wildland fire use or WFU) in two Sierra Nevada wilderness areas. We present reconstructions of historical fire occurrence using tree ring proxies, along with chronologies of tree recruitment, to infer the effects of WFU programs on forest structure. Historically, fires burned every 6 to 9 years, which moderated tree recruitment. Fire suppression policies established in the early 1900s successfully excluded fire and allowed for unprecedented tree recruitment. Despite the substantial changes in forest structure and composition, the frequency and extent of fires during the current WFU period (1972–present) approach historical levels. This information can provide some necessary insight in implementing WFU policy and developing management plans for similar forest types throughout the western US. [ABSTRACT FROM AUTHOR]