Estimating the annual diametric increment in a natural Rainforest in south Brazil

Abstract

Diametric increment is a complex variable to be estimated in natural forests, especially given species composition and slow tree growth. In these situations, some studies have turned their attention to the use of individual tree growth models combined with strategies for grouping trees or species. This work aimed to estimate the diametric increment of trees in a natural remnant of a natural Rainforest in south Brazil, aiming to investigate methodologies for forming groups of individuals that favor the estimation of individual diametric increment. The groups were formed based on a two-stage methodology, based on relative diameter, diametric increment, and competition indexes. The diametric increment was estimated based on a ratio estimator used to reconcile the grouping strategy. The grouping method satisfactorily classified the individuals, in which the competition indexes were relevant for this classification. The estimation error of the diametric increment was 0.0599 cm.year-1 for the training data and 0.0765 cm.year-1 for the validation data. The estimate of the future diameter had an average error of 4.52%. The combination of a two-stage stratification and ratio estimator was satisfactory for accurately estimating the diameter increments of all tree species.