Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests.

摘要

Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems of the Sierra Nevada (California), resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a mixed-coniferforest and investigates how silvicultural and fuels treatments affect potential fire behaviour. The computer program FARSITE was used to model fire growth and behaviour spatially and temporally. Fire modelling was performed in the North Crane Creek watershed of Yosemite National Park. Treatments were simulated by adjusting fuel (total load, load-by-size class, depth), height-to-live crown base, tree height, and crown density parameters. Treatments modelled included prescribed burn, pile and burn, cut and scatter, thinning and biomass (removal), thinning and biomass followed by prescribed burn, and salvage or group selection harvest with and without slash and landscape-level fuel treatment. The prescribed burn, thinning and biomassing followed by prescribed burn, and salvage or group selection with slash and landscape fuel treatments, resulted in the lowest average fireline intensities, heat per unit area, rate of spread, area burned, and scorch heights. Cut and scatter, salvage or group selection treatments that do not treat slash fuels resulted in fire behaviour that is more extreme than the untreated forest. It is emphasized that restoration of mixed-conifer ecosystems must include an examination of how proposed treatments affect fuel structures.