Evaluation of a Loblolly Pine Plantation Thinning Model

Abstract

Abstract Eight long-term thinning studies of loblolly pine in plantations, established across the range of loblolly pine, are summarized for purposes of evaluation of a thinning model. The studies have been classified according to questions they addressed, such as intensity of selective thinning, intensity of row thinning, row versus selective thinning, and accelerated saw-timber production. Based on these studies the following inferences are made: 1. With selective thinning, total yield decreases and final stem size increases as intensity is increased. As rotation length is increased, the loss in total yield associated with increased intensity is diminished. 2. Row thinning, without successive selective thinning, reduces total yield proportional to the intensity of thinning, has little effect on average diameter, but significantly increases the diameter of dominant trees. 3. Row thinning combined with moderate to heavy selective thinning results in responses little different than from selective thinning alone. 4. With heavy early thinning, yields of 15 + Mbf are attainable in a 30 year rotation. Since the studies were not used in the development of the mathematical model being evaluated, they represent an independent test of the model. Thinning simulations based on the loblolly pine plantation growth and yield. model are compared with the reported observations from the eight studies, the intent being to test the veracity of the model with respect to its accuracy of prediction and consistency with regard to the inferences suggested by the studies. The comparisons presented demonstrate that the model performs well with regard to both accuracy and consistency. Recognizing that the studies were, in general, established under conditions much different than occur today, use of the model to expand the applicability of the inferences implied from the studies to current conditions is demonstrated.