Potential wildfire and carbon stability in frequent‐fire forests in the Sierra Nevada: trade‐offs from a long‐term study

Abstract

AbstractForests are the largest terrestrial carbon stock, and disturbance regimes can have large effects on the structure and function of forests. Many dry temperate forests in the western United States are adapted to a regime of frequent, low‐to‐moderate severity fire. The disruption of this disturbance regime over the last century has shifted forest conditions, making them more susceptible to high‐severity fire. Fuel treatments have been shown to effectively reduce wildfire hazard, often with co‐benefits to ecological values. However, the effects of fuel treatments on forest carbon are complex, often characterized by direct costs (e.g., carbon emissions from prescribed fire) and wildfire‐contingent benefits (increased resistance of live tree carbon to wildfire). In this study, we employ risk‐sensitive carbon accounting and empirical data from a replicated field experiment to evaluate the stand‐scale carbon effects of four management regimes over a 14‐yr period in a historically frequent‐fire adapted forest. All three active treatment regimes immediately increased stable live tree carbon stocks over no‐treatment controls. In most contexts examined, mechanical‐only or no‐treatment controls will maximize expected total carbon stocks when incorporating wildfire risk and the carbon stability of live biomass, dead biomass, and offsite forest products, although we acknowledge our wildfire modeling may underestimate C losses, particularly in the control stands. Undoubtedly, many other ecosystem and social values besides carbon will be important factors that influence fuel and restoration treatments.