THE RED-COCKADED WOODPECKER'S ROLE IN THE SOUTHERN PINE ECOSYSTEM, POPULATION TRENDS AND RELATIONSHIPS WITH SOUTHERN PINE BEETLES

摘要

This study reviews the overall ecological role of the Red-cockaded Woodpecker (Picoides borealis) in the southern pine ecosystem. It is the only North American woodpecker species to become well adapted to a landscape that was relatively devoid of the substrate typically used by woodpeckers for cavity excavation (i.e. snags and decayed, living hardwoods). Its adaptation to use living pines for cavity excavation has expanded the use of this fire-disclimax ecosystem for numerous other cavity-using species. As such, the Red-cockaded Woodpecker represents an important keystone species of fire-disclimax pine ecosystems of the South. Historically, populations of this woodpecker and other cavity dependent species decreased dramatically with the logging of the southern pine forests between 1870 and 1930. Woodpecker populations continued to decline into the 1980s as a result of inadequate old-growth pine habitat, and suppression of fire which permitted encroachment of hardwoods into the previously pine-dominated ecosystem. Management practices initiated after 1988 have resulted in woodpecker population increases on Texas national forests. Cavity-tree mortality and southern pine beetle (Dendroctonus frontalis) infestation of cavity trees on the Angelina National Forest in eastern Texas were studied from 1983 through 1996. The intensive management activities initiated to stabilize severely declining woodpecker populations in 1989 may have increased beetle infestation rates of cavity trees in loblolly (Pinus taeda) and shortleaf (Pinus echinata) pine habitat resulting in a net loss of cavity trees over the past seven years. Initial results suggest that beetle-caused mortality of cavity trees may be related in part to ambient southern pine beetle population levels in surrounding forest stands.