Snag dynamics and cavity occurrence in the South Carolina Piedmont

Abstract

Standing dead trees, or snags, are natural components of forest stands and are important habitats for many wildlife species. We examined snag dynamics from 1982–1990 on 140 0.1ha plots in the upper Piedmont of South Carolina. Plots were established in 10 stand type–age class combinations. Mean snag density was 28.4snags/ha and mean snag diameter (DBH) and height were 20.3cm and 9.9m, respectively. Highest snag densities occurred in hardwood stand types; pine plantations had lower (p≤0.05) snag density than all other types. Within a particular stand type, snag densities, recruitment rates, and loss rates generally were lowest in the oldest age classes. Intermediate age classes of all stand types had higher snag densities and snag turnover rates than younger or older stands within that type. Young pine plantations had the lowest recruitment rate (x̄=1.79snags/ha/year) and old pine plantations had the lowest loss rate (x̄=1.59snags/ha/year) of all the stand type–age class combinations. Although twenty species of snags were observed, five species/species groups, shortleaf pine (Pinus echinata), red oaks (Quercus spp. ), white oaks (Quercus spp. ), loblolly pine (P. taeda), and yellow poplar (Liriodendron tulipifera), occurred most frequently. Snag DBH and cavities/snag were not significantly correlated. Stage of decay for cavity and noncavity snags (r=0.97 and 0.83, respectively; p≤0.05) and number of cavities/snag (r=0.78) increased with year since snag recruitment. Ten snag species contained cavities (x̄=0.1 cavities/snag), but shortleaf pine accounted for 56% of the cavity years observed (x̄=0.18cavities/snag). Three other softwood species also contained equal to or above average numbers of cavities/snag. Approximately 30% of all snags fell within two years of recruitment, 55% within three years, and 95% within six years. Snag longevity was independent of diameter class (p=0.67). Hardwood snags, especially those in upland hardwood stands, appeared to persist longer than pine snags. As pine plantations managed on short rotations (<25 years) and older-aged stands (>50 years) of all types may not provide abundant snags in the South Carolina Piedmont, the potential for wildlife habitat might be enhanced if older, larger diameter trees, especially softwood species, are retained or designated as snag replacements.