Stand development and growth responses of 1- and 3-year-old natural upland hardwoods to silvicultural treatments.

摘要

Intense competition for growth resources between herbaceous and woody vegetation is considered a major constraint to the growth and development of newly regenerated forest stands. However, very few studies have explored silvicultural opportunities to manage these constraints. In this study, the effects of fertilizer application, density and vegetation control on rising 1- and 3-year-old upland mixed species North Carolina Piedmont stands were monitored for 3 years following the imposition of treatments. Two upland sites were studied: (1) Hill Demonstration Forest - a natural 2 ha loblolly (Pinus taeda) and Virginia pine (P. virginiana) stand with a lesser component of mixed hardwoods; and (2) Duke Forest - a 5 ha mature natural mixed hardwood stand with Quercus spp. predominating. Treatments include: weeding by repeated hand removal, NPK fertilizer application and thinning by reducing woody stem density to 4 stems/plot, consisting of two yellow poplars (Liriodendron tulipifera) and two red or white oaks (Q. alba, Q. falcata, Q. rubra, Q. stellata or Q. velutina). Broadcast fertilizer application proved very beneficial in accelerating stem growth and promoting self-thinning at both sites. Weeding (non-arborescent vegetation) treatments without thinning had no effect on stem height. At both sites, substantial increases in tree size were noted for yellow-poplar and oaks when thinning and weeding treatments were combined. A significant fertilizer application effect on thinned plots was also noted for oaks. These results demonstrate that stem growth and stand development are constrained by the availability of site growth resources, and can be silviculturally managed to promote stand development..