Predicting survival and growth rates for individual loblolly pine trees from light capture estimates

Light capture estimates from models can be related to survival and growth rates and may provide new ways to model forest dynamics. However, relationships between light capture, growth, and survival should vary widely with tree age, site conditions, and stand density, so predictions from light capture models need to be tested over a range of stand conditions. We used the tRAYci stand light model (A. Brunner. 1998. For. Ecol. Manage. 107: 19-46) to estimate weighted leaf area (WLA), an estimate of annual light capture, for every tree, in 36 even-aged loblolly pine (Pinus taeda L.) stands, representing different combinations of site index and planting density, over an 8-year period. We also developed regression equations relating light capture estimates to height growth, basal area growth, stem volume growth, and survival probability for individual trees at different ages, sites, and planting densities. Our results suggest a significant correlation between estimates of WLA and tree growth and survival rates, and that the tRAYci model is robust across a range of stand conditions. An important finding was that WLA was a better predictor of survival probability than measured basal area increment. Effects of site index, age, and planting density on light capture - growth relationships are also discussed.