Long-term effectiveness of fuel treatments in oak and chaparral stands of Northern California

Fuel reduction treatments are broadly implemented to reduce the risk of extreme wildfire. Yet, research on the long-term effectiveness and ecological consequences among these treatments is lacking. In this study, I examined short- and long-term changes in fuels and understory vegetation after treatment in chaparral and oak-dominated stands of Whiskeytown National Recreation Area. Treatments included mastication and spring burning, spring burning only, mastication only, and hand-thinning. Treatments were applied randomly to 1 to 2 units within each of 10 blocks. Two plots were established in each treatment unit and fuel and vegetation data was collected and analyzed at the block level (n=10). Results showed all treatments, except spring burn only, reduced live shrub height compared to the control. The combined mastication and spring burn treatment had up to 2.3 times higher live shrub density than the other treatments. Mechanical or manual only treatments promoted reductions in fine dead woody surface fuel loading compared to the control 15 years after treatment. There were subtle changes in the understory plant community, including an increase in species richness in the mastication and spring burn treatment and a decrease in species richness over time. The effects of fuel treatments on fuels and understory vegetation were highly varied with some level of trade-off in effectiveness. Optimal fuel treatments will likely depend on the specific site objectives. However, results from this study indicate that mastication and hand removal treatments can provide substantial decreases in live and dead fuel loading over the long- term without substantial changes to the understory plant community