Parametrização e calibração do modelo 3-pg para dois clones de eucalipto cultivados em diferentes densidades populacionais

Abstract

In the state of Alagoas, around 18.700 hectares are destined to the production of eucalyptus, with plantations cultivated in different edaphoclimatic conditions. Several factors affect the ecophysiological processes of trees and forest productivity (water and nutritional availability, population density, silvicultural treatments and local edaphoclimatic conditions), due to the genotype-environment interaction. Models based on ecophysiological processes are useful tools to assist in the planning of forest companies, as they correlate such factors to generate yields from forest productivity. Therefore, the present work aimed to evaluate the efficiency of the 3-PG model in eucalyptus clones cultivated in Alagoas under different planting densities. The model was tested for the Zona da Mata region of Alagoas, which concentrates forest crops in the state, with data from a controlled experiment in the municipality of Rio Largo. The parameterization was carried out using the experiment's database together with the bibliographical research considering similar cultivation conditions and genetic material while the therapy was performed manually considering the amplitude observed in the literature, of the criteria received in the model. With the model parameterized and calibrated, simulations were performed to estimate the growth of total height (h), diameter at breast height (d), volume (v) and average annual wood increment (IMA) of two clones of eucalyptus (I144 and VE41) grown at three population densities (1,666, 1,111 and 833 plants per hectare). The accuracy of the model was verified through graphical analysis, intuitive linear (R), direction coordinate (R2), absolute (Sxy) and relative (Sxy%) patterns and model efficiency. Graphically, the values estimated by the 3-PG model for the variables total, diameter at breast height, volume and average annual wood increment, approximated the heights observed in the field. In evaluating the efficiency of the model, the estimated values did not differ statistically from the measured values, with the exception of the treatment of clone I144 under the planting density of 833 arv.ha-1. It is concluded that the 3-PG model is efficient to estimate the variables h, d, v and IMA of the two clones and three spacings tested in the study region.

Key words: eucalyptus culture; ecophysiological model; forest planning.