Legacies of recent disturbance history on post-fire regeneration of a subalpine forest

Natural disturbances, such as fire and wind, in forest ecosystems can restore landscape heterogeneity and structural complexity important to sustaining forest vitality and economic resources. However, disturbances occurring in rapid succession may reduce environmental quality to such a degree that forest recovery is severely delayed or aborted altogether, leading to meadow communities. The goal of our research is to understand the interactive effects of multiple disturbances on the regeneration dynamics and landscape structure of managed subalpine forest ecosystems. Our study area in Colorado's Routt National Forest experienced a large blowdown in 1997, salvage logging in 1999-2001, and a severe fire in 2002. In the summer of 2006, we inventoried tree seedling regeneration, understory vegetation, coarse woody debris (CWD), and soil temperature in burned areas with different pre-fire disturbance. The highest abundance and frequency of understory species occurred in fire-only sites, whereas lowest values occurred in fire/blowdown sites. Seedling regeneration was significantly greater in fire-only sites and very infrequent in fire/logged/blowdown areas. Size distributions of CWD varied substantially with treatment. Soil shaded by CWD had significantly reduced temperatures, but ranges in temperature were much larger in exposed areas within sites disturbed prior to fire. Relatively rapid sequencing of severe disturbance followed by fire in subalpine forest appears to create more extreme environmental conditions than those created by fire alone and may delay forest regeneration. Remote sensing is used to extrapolate our field measurements to the larger region and for comparison with USFS fire severity maps.