Abstract
The aim if this work was to assess and propose projection models for diameter at breast height and total height of individual pine trees and the contribution of competition indexes in these models. Data was obtained from 1056 permanent sampling units of non-thinned Pinus taeda L. stands located in the Telêmaco Borba region, Paraná, Brazil, with ages between 3.4 and 19.5 years. In order to project the diameter and total height of the trees, linear models were tested according to the variable in the current age, the projection age in the future, the basal area, and the site index, as well as their transformations. The Spearman correlation was obtained between competition indexes and dendrometric and stand variables, with the GH (Glover and Hool), LO (Lorimer) and ST (Stage) indexes being selected. These indexes were assessed as independent variables in the models, whose contributions were verified through the “F ci ” test on the incremental contribution. The models were assessed through the adjusted coefficient of determination, standard error of the estimate, and boxplots of residuals. The models provided precise and bias-free projections. The competition indexes statistically contributed to diameter and total height projection according to the “F ci ” test, increasing the precision of projected values for the majority of models tested. The indexes with major contributions to individual tree modelling for diameter and total height projection of Pinus taeda were Glover and Hool (GH) and Lorimer (LO), respectively.
Highlights
Growth and production models for individual trees have great flexibility and characterize in a precise manner the growth of stands under several conditions with detailed results (WEISKITTEL et al, 2011) such as stand structure and dynamics
Based on the results found, model 1, which used the competition index Glover and Hool (GH), provided the best statistical results
It is likely that one or other model would provide similar results. It can be a reflex of the high correlation between the competition indexes and the diameter measured in the current age, since these indexes are obtained according to this variable
Summary
Growth and production models for individual trees have great flexibility and characterize in a precise manner the growth of stands under several conditions with detailed results (WEISKITTEL et al, 2011) such as stand structure and dynamics. In the simulation of growth by individual tree modelling, the information about diameter at breast height and total height are usually used due to their strong correlation with total volume of trees (WEISKITTEL et al, 2011). This modelling can be subdivided into distance-dependent, independent, and semi-dependent models (CONTRERAS et al, 2011).
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