The effects of precommercial thinning and midstory-control on the flora and fauna of young longleaf pine plantations

Abstract

I examined the effects of longleaf pine (Pinus palustris) restoration using plantation silviculture on the avian, small mammal, and herpetofauna communities on the Savannah River Site, a National Environmental Research Park near Aiken, South Carolina. Vertebrate populations were surveyed from 1995 through 2003 on a series of plantations that had been precommercially thinned and/or received midstory-control via herbicides between 1994 and 1996. Understory and overstory vegetation was surveyed from 1994 through 2004. Thinning and midstory vegetation reduction treatments had greater herbaceous cover than the control through 2004 after a 1-2 year decline on midstory-control plots. Initially, thinned plots had the greatest herbaceous cover. However from 1998 through 2004, the combined treatment had the most herbaceous cover. Without midstory-control, thinning released midstory hardwoods. The effect of thinning or midstory-control alone on bird abundance was positive but short-lived. The positive effects were larger and persisted longer on combined treatment plots. My results indicate that precommercial thinning longleaf plantations, particularly when combined with midstory-control and prescribed fire, had a modest beneficial impact on avian communities by developing stand conditions more typical of natural longleaf stands maintained by periodic fire. All treatments resulted in short-term increases in small mammal abundance, but effects were minimal by 5-7 years after treatment. By 2001, pine basal area had returned to pre-treatment levels on thinned plots suggesting that frequent thinning may be required to maintain abundant and diverse small mammal communities in longleaf pine plantations. I did not detect any treatment related differences in herpetofauna abundance. These results suggest that restoring longleaf with a combination of precommercial thinning, midstory-control with herbicides, and prescribed fire can have a short-term positive effect on the avian and small mammal communities without affecting the herpetofauna community. However, periodic thinnings may be necessary to extend the positive effects. ®®®