A New Diameter Distribution Model for Unmanaged Loblolly Pine Plantations in East Texas

摘要

A parameter recovery procedure for the Weibull distribution function based on four percentile equations was used to develop a diameter distribution yield prediction model for unmanaged loblolly pine (Tinus taeda L.) plantations in East Texas. This model was compared with the diameter distribution models of Lenhart and Knowe, which have been used in East Texas. All three models were evaluated with independent observed data. The model developed in this study performed better than the other two models in prediction of trees per acre and cubic-foot volume per acre (wood and bark, excluding stump) across diameter classes. Lenhart's model consistently underestimated the larger-diameter classes because it was developed originally with data mostly collectedin young plantations. Knowe's model overestimated volume in sawtimber-sized trees, which could lead to over estimations of volume in older loblolly pine plantations found in East Texas. An example also is provided to show users how to use this new yieldprediction system. These results support the recommendation that forest managers should use growth and yield models designed and/or calibrated for the region in which they are implemented.