Growth and yield model comparisons for mid-rotation loblolly pine (Pinus taeda L.) plantations in the southeastern US

Growth and yield models are important tools for forest managers. This study compares six models used for loblolly pine plantations in the southeastern US including the Plantation Management Research Cooperative's (PMRC) 1996, 2004 and 2014 models, the Loblolly Decision Support System (LobDSS v. 3.0.1.3), PTAEDA (v. 4.0.11) and ForesTech International's Simulator for Managed Stands (SiMS v. 2009). Model runs were initiated using pre- and post-thin measurement values from first-thinned, Piedmont/Upper Coastal Plain installations of the PMRC's Mid-rotation Treatment (MRT) Study and were then evaluated using the re-measurement data at 2, 4 and 6 years since treatment (YST). Several plots used in this analysis incorporate mid-rotation treatments including thinning and fertilization; these treatments were incorporated into the appropriate model simulations. Three fit statistics were used to compare model outputs to measured MRT values. A linear mixed-effects model was estimated to compare model green weight (GWT) outputs across the different treatment and YST combinations. Results revealed that GWT estimates from LobDSS, SiMS and the PMRC 2004 and 2014 models were not statistically different from each other or the MRT data GWT estimates. GWT estimates from PTAEDA and the PMRC 1996 models were significantly different from the other four models. Overall, these findings support land managers confidence in growth and yield models and their use for managed stands.