Simulated fire regimes favor oak and pine but affect carbon stocks in mixed oak forests in Pennsylvania, USA

Changes in fire regimes can alter patterns of species dominance and forest carbon stocks by amplifying or diminishing fire vegetation feedbacks. The combined influence of 19th century forest harvesting followed by 20th century fire exclusion has caused a shift in species composition in fire adapted mixed oak forests toward fire sensitive shade tolerant hardwoods that reduce flammability of surface fuels. Prescribed fire is a tool with potential to restore fire adapted oak forests with a history of fire exclusion, but outcomes from the practice of prescribed burning are unclear due to a paucity of studies that apply prescribed fire over multi decadal periods. Here we use simulation modeling to investigate how variation in fire frequencies and period of burning influence simulated dominance of oak, pine, and other hardwoods and forest carbon stocks in Pennsylvania mixed oak forests. Single burns had little effect on basal area (BA) or species composition while more frequent burning increased pine BA, especially when pine was initially abundant. Simulated fire regimes with fire intervals of 10-20 years applied for multiple decades maintained high oak BA and reduced fire sensitive hardwoods. Average BA at the end the 60-year simulation period was inversely related to fire frequency and live carbon stocks decreased with more frequent burning. Simulated fire effects suggest implementation of prescribed fire regimes over periods of decades may be a feasible strategy to maintain or increase oak and pine dominance where management objectives are compatible with fire use. Moreover, several simulated fire regimes seem capable of maintaining BA of fire adapted species and maintaining or increasing overall live C stocks providing a range of management options for maintaining oak and pine, and live carbon stocks using prescribed fire.