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Abstract
Plots at eleven installations of first-thinned loblolly pine plantations were left without second thinning or second-thinned and received no additional fertilization, chemical release, or fertilization plus release treatments. Eight-year post-treatment effects on pine stemwood growth and product class yield and hardwood development were examined. Eight-year absolute total green weight growth was greatest for second thinned, fertilized and released stands (68 tons ac-1) and least on second thinned only stands (56 tons ac-1). Green weight growth was intermediate for second-thinned released (64 tons ac-1) and second thinned fertilized stands (61 tons ac-1). There were no significant fertilization by release interactions for periodic growth measures. The release treatment main effect was significant for DBH, total green weight and volume growth for at least one post-treatment period. The fertilization treatment main effect was only significant for DBH growth. Relative growth in loblolly pine total green weight was significantly greater on second-thinned stands with or without additional treatments compared to the non-second thinned stands. The lack of difference between fertilization and release treatment effect on total green weight growth, suggests access to nutrients is as important as absence of nutrients within the study sites at mid-rotation. Site and environmental variables were examined for their influence on plantation response six-years post-treatment. Average standardized change in volume was influenced by average percent clay, initial small wood root stock ac-1, average annual precipitation yr-6, and available water storage capacity.