Recovery of herb-layer vegetation and soil properties after pile burning in a Midwestern oak woodland

Thinning and removal of woody vegetation is the first step in restoring ecosystem structure to systems altered by woody encroachment. However, pile burning-a common method of eliminating woody residue at restoration sites-can promote the establishment of exotic species and adversely impact soils and native vegetation via extreme soil heating. Despite its widespread use, pile burning effects remain poorly understood in oak woodlands compared to coniferous forests. We examined how pile burning influenced soil properties and herb-layer recovery in a Midwestern, U.S. oak woodland undergoing restoration via exotic shrub removal, tree thinning, and prescribed burning. We quantified soil properties and passive vegetation recovery inside and adjacent to pile burn scars after 3 years, and tested whether native seed additions in year 1 increased native cover and reduced exotic cover in year 3. Bare ground cover, soil pH, and concentrations of P and Ca remained elevated 3 years after pile burning. In contrast, native cover, native richness, and floristic quality recovered to levels similar to adjacent control locations. Pile burning did not promote exotic invasions, increase inorganic forms of N, or alter patterns of the native cover of most growth forms. However, Carex species failed to reestablish in burn scars. Compared to passive recovery, seed additions increased native cover in burn scars and reduced exotic cover in adjacent control locations. Our results indicate that burn scars can naturally recover in oak woodland, but native seed additions may accelerate this process and improve restoration outcomes.