CONSTRAINING INDIVIDUAL TREE DIAMETER INCREMENT AND SURVIVAL MODELS FOR LOBLOLLY-PINE PLANTATIONS

Among extant forest growth and yield models, individual tree growth mo dels provide the most detailed information, which is useful for intens ive forest management. However, individual tree growth models may be i naccurate for stand-level predictions because of the cumulative error resulting from individual tree predictions. This paper is aimed at dev eloping a method to ensure that individual tree growth models not only provide precise individual tree predictions but also give precise sta nd-level estimation. Based on the conceptual relationships between bas al area of each diameter class and the diameter increment of trees in the same diameter class, a constrained regression equation system is p roposed. The same approach is also applied to modeling individual tree survival probability. An algorithm for estimating multiresponse regre ssions was developed. Results using data from unthinned loblolly pine (Pinus taeda L.) plantations show that the simultaneous equation syste m provides nearly the same individual tree diameter increment estimate s as the unconstrained model but better estimates for basal area of ea ch diameter class and for total stand basal area. The potential for im proving stand mortality estimation with a constrained individual tree survival model where there is little mortality in the data is limited.