Effects of Opening Size and Site Preparation Method on Vegetation Development after Implementing Group Selection in a Pine-hardwood Stand

Three opening sizes (0.25, 0.625, and 1.0 ac) and three site preparation methods (herbicides, mechanical, and an untreated control) were tested in a pine-hardwood stand dominated by loblolly and shortleaf pines ( Pinus taeda L. and P. echinata Mill.) and mixed oaks ( Quercus spp.) that was being converted to uneven-aged structure using group selection. The study was a 3x3 factorial in a randomized co mplete block design with three replicates. Site preparation in the openings was delayed for 2 years after harvest until an ad equate pine seed crop was forecast. At 3 years after the group-selection cut and 1 year after site preparation, pine seedling stocking was higher ( P=0.01) in the 0.25-ac openings (89%) when compared to the 0.625-ac openings (71%) or the 1.0-ac openings (66%). Mechanical site preparation resulted in higher (P=0.03) pine seedling density (5,272 stems/ac) compared to the control (2,490 stems/ac) or chemical site preparation (3,044 stems/ac), but both the mechanical and chemical treatments had better ( P=0.03) stocking (82%) of pine seedlings than the control (61%). Both mechanical and chemical site preparation were effective in reducing (P<0.0\) the density (85% less) and stocking (75% less) of nonpine woody saplings compared to the control, but size of opening had no effect on density of nonpine woody seedlings or saplings at 1 year after site preparation.