STRUCTURE OF MIXED PINE AND HARDWOOD STANDS 12 YEARS AFTER VARIOUS METHODS AND INTENSITIES OF SITE PREPARATION IN THE GEORGIA PIEDMONT

In the Georgia Piedmont (U.S.A.), size, abundance, and species diversi ty of trees were quantified in a plantation of Pinus taeda L. 12 years after various methods and intensities of site preparation. In clear-c ut only versus site-prepared plots, greater hardwood abundance (27% vs . 8% of the total basal area) and size (8.6 vs. 7.4 m in height) were associated with reduced pine volume (73 vs. 123 m(3)/ha) and increased Simpson and Shannon diversity indices. Tree-species richness was grea ter in plots where residual trees from clear-cutting had been removed with a chainsaw versus large machinery (10 vs. 7 species). With increa sing site-preparation intensity, reductions in basal area of volunteer pines coincided with proportionate increases (R(2) = 0.80) in basal a rea of planted pines. As a result of this compensatory effect, total v olume of all pines varied little (122-134 m(3)/ha) among site-preparat ion intensities. Research results suggest that site-preparation treatm ents can be selected to facilitate the development of a variety of sta nd structures, including those that favor evenness (clear-cut only) or richness (manual cutting) of tree species, low-cost production of pin e fiber (manual cutting), and stand uniformity for management of pine sawtimber (mechanical and herbicide).