Biological constraints on the growth of hardwood regeneration in upland Piedmont forests

Abstract

The effects of aboveground fungi, insects, browsing mammals and weeds on the growth (height, diameter and volume index) and density of hardwood stems were studied on three upland sites in the Piedmont of North Carolina, USA during the first two growing seasons following clearcutting. Competition from weeds was the most detrimental to hardwood growth. Pesticide treatments alone (broad-spectrum insecticide, fungicide and mammal repellent) did not significantly increase growth. Compared to the control (no weeding or pesticides), stems receiving the pesticide+weeded treatment increased in height 1.6–4.5 times, diameter 1.7–5.3 times and volume index 3.4–5.1 times by the end of second growing season, across all sites. Stem density did not exhibit clear treatment effects, although individual tree mortality and recruitment in the plots were not recorded. Exclosures, with weeding, to eliminate the browsing impact of white-tailed deer ( Odocoileus virginianus Zimmermann), installed only during the second year of study, yielded a 1.9, 1.6 and 3.2 times increase in mean stem height, diameter and stem volume index, respectively, as compared to weeded only plots. Results indicate that very young hardwood regeneration can respond quickly to release from biological constraints and the rate of stand establishment and development may be enhanced with stand manipulations in the first two growing seasons.