Demographic responses of shrews to removal of coarse woody debris in a managed pine forest

Abstract

We trapped shrews at six 9.3 ha plots from which logs ≥10 cm diameter (coarse woody debris; CWD) had been manually removed and six control plots in managed loblolly pine ( Pinus taeda) forests of the southeastern coastal plain, USA. Trapping was conducted seasonally between autumn 1997 and summer 2001. Capture rates of Cryptotis parva were lower at plots from which CWD was removed than at control plots ( P=0.011) and declined at all plots over the study period ( P<0.001). Capture rates of Blarina carolinensis ( P=0.129) and Sorex longirostris ( P=0.432) did not differ between removal and control plots, but declined over the study period ( P<0.001). Age distributions of B. carolinensis differed between removal and control plots ( P=0.048) with a smaller proportion of individuals in young age categories at removal plots. Sensitivity of Cryptotis to the removal of CWD may have been due to its sociality or low population density at the study area. A reduction in the abundance of young B. carolinensis after removal of CWD may reflect reduced reproduction and immigration of older individuals from outside the plot. Effect of removal of CWD on populations of these shrews was relatively weak compared to strong seasonal and multi-year variation in abundance. However, weak treatment effects may have been partly due to low ambient levels of CWD at control plots.