Fire History in Diamond Mountains, Lassen National Forest, Northern California
Lisa Gill
Fire is an ecologically significant process in the fire-prone ponderosa pine and mixed conifer forests in the northern Sierra Nevada’s. Spatiotemporal variations in fire regimes are controlled by processes that operate over a range of scales and these can be broadly grouped as bottom-up (e.g. topography) or top-down (e.g. climate and human land use patterns) controls. We quantified spatial and temporal variability in fire regimes in ponderosa pine and mixed conifer forests in northeastern California to identify the relative influence of bottom-up versus top-down controls in this region. Dendroecological methods were used to quantify pre-suppression era fire regimes (i.e. frequency, return interval, season, and extent) from samples (n = 214) of fire scarred trees. Top-down controls, specifically interannual climate variability and human land use patterns, strongly influence fire regimes. Synchronization of fire across the landscape, and fire-free years, were associated with interannual climate variability. Large-scale cessation of fire beginning in the mid 19th century and continuing through present was seen following Euro-American settlement and implementation of the 1905 U.S. fire exclusion policy. Fire regimes were also influenced by bottom-up controls, specifically elevation and forest composition. Fires return intervals were shorter and fire burned earlier in the season on pine-dominated low elevation forests than on high elevation fir-dominated mixed conifer forests.
This project was supported with funding from the National Forest Service
