| Managing forests with multiple ages and size classes can promote both economic and ecological services. Interest among landowners in managing for multiple uses under structurally diverse uneven-aged management has increased recently in Florida (USA), partly due to a trend toward public landownership. Increasingly, forest managers and land owners are interested in converting structurally homogenous plantations into more diverse conditions commonly found in uneven-aged stands. The objective of the present study is to assist in this process by developing growth, mortality and recruitment models for slash pine (Pinus elliotti. var. elliottii) in Florida, and also to use these models to demonstrate the use of a simulation model to test harvesting regimes such as thinnings, single tree selection and group selection. The regimes were evaluated based on their utility in achieving a set of desirable structural characteristics. Using 70 permanent plots in natural and plantation forests, we developed diameter and height growth, recruitment and mortality models. We used a mixed modeling approach, comparing linear and non-linear mixed models. Models were evaluated with information criteria, bias, and precision measures. Due to the unavailability of an independent dataset, we validated the models using a leave-one-out cross validation. Our results indicated that the mixed models produced better estimates of growth versus fixed effects models. A Mixed model also gave better probability estimates of mortality than a fixed effects model. Probability of recruitment was best estimated with logistic regression with number recruited conditionally with a generalized Poisson regression. Simulation results demonstrated that light thinning, heavy thinning, and group selection could be useful for the conversion process. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)... |
