Wildlife Restoration via Forest Management in Fire-Suppressed Longleaf Pine Sandhills.

摘要

The once-extensive longleaf pine (Pinus palustris) ecosystem of the southeastern United States has been reduced to a fraction of its historic extent. A fire-adapted system, many remaining fragments have been fire-suppressed and invaded by hardwood trees, particularly oaks (Quercus spp.). This change in species composition alters the habitat and is to the detriment of wildlife assemblages associated with longleaf pine forests. Fire surrogates and prescribed burning have been suggested as potential management strategies to restore fire-suppressed and hardwood-invaded longleaf pine forests to target conditions; due to the unique effects of fire, it is generally suggested that prescribed burning should follow application of any hardwood removal treatment. To determine whether fire surrogates followed by prescribed burning affected wildlife populations and assemblages, we sampled for birds and reptiles within 20 experimental sites and six reference sites. Experimental sites were initially subjected to either mechanical hardwood removal followed by fire, herbicide application followed by fire, prescribed burning alone, or remained in a fire-suppressed state (i.e., controls). Following initial treatment, all sites experienced over a decade of prescribed burning on an approximately two-year interval. We evaluated the effects of a given treatment by comparison of wildlife populations and assemblages on treatment sites to those on reference sites initially and also after over a decade of prescribed burning. If conditions associated with a given treatment were indistinguishable from those of reference sites, we considered this as evidence that management objectives were met. Over the long-term, application of herbicide followed by prescribed burning was the only method that restored bird assemblages to the reference condition, although species positively associated with longleaf pine in reference condition responded positively to all treatments. Occupancy probabilities for these species on all treatment sites were indistinguishable from those on reference sites by the conclusion of the study. Initially, reptile assemblages within treatment sites treated with prescribed burning alone were most similar to those of reference sites; fire surrogates did not immediately provide an observed benefit. At the conclusion of the study, reptile assemblages at all sites were indistinguishable from those on reference sites except for assemblages on sites treated with herbicide, suggesting herbicide application was relatively ineffective at restoring reptile assemblages. A mark-recapture study of the six-lined racerunner (Aspidoscelis sexlineatus) also identified prescribed burning as effective. Initially, abundances on sites treated with prescribed burning alone, as well as on sites treated with mechanical hardwood removal followed by fire, were comparable to abundances within reference sites. Over time, abundances at all sites were comparable to those on reference sites. Overall, effective restoration of wildlife populations and assemblages in fire-suppressed longleaf pine sandhills was achieved and prescribed burning over approximately a decade was generally sufficient to achieve this result. In general, there was little observed benefit or need to employ fire surrogates prior to prescribed burning.