Vegetation Recovery in Slash-Pile Scars Following Conifer Removal in a Grassland-Restoration Experiment

A principal challenge to restoring tree-invaded grasslandsis the removal of woody biomass. Burning of slash pilesto reduce woody residues from forest restoration practicesgenerates intense, prolonged heating, with adverse effectson soils and vegetation. In this study, we examined vegetationresponses to pile burning following tree removalfrom conifer-invaded grasslands of the Oregon Cascades.We quantified the longevity and magnitude of fire effectsby comparing ground conditions and the cover and richnessof plant species in burn-scar centers (higher-intensityfire) and edges (lower-intensity fire) with adjacent unburnedvegetation 7 years after treatment. We interpreted patternsof recovery through the responses of species with differinggrowth forms, habitat affinities, and clonality. Cover of bareground remained elevated at the centers, but not at the edgesof scars; however, much of this effect was due to gopherdisturbance. Total plant cover, consisting entirely of nativespecies, was comparable in and adjacent to scars. However,richness remained depressed at the scar centers. Cover ofgrass, meadow, and non-clonal species was comparable inand adjacent to scars, but cover of forb, sedge, residual forest,and clonal species was reduced at the centers. Althoughscar centers had a simpler community structure (fewer butmore abundant species) than the adjacent vegetation, theyremained free of exotics and recovered quickly, aided bythe soil-disturbing activities of gophers and the regenerativetraits of native, disturbance-adapted species. Pile burningcan be a viable and efficient approach to fuel reduction inthe absence of exotics.