Características dendrométricas, aspectos silviculturais e produtividade de plantios de Hevea guianensis Aubl. na Floresta Nacional do Tapajós, estado do Pará.

Abstract

In the Tapajós National Forest, a Conservation Unit located in the western part of the State of Pará, Northern Brazil, there is a common practice among riparians that consists of the extraction of latex from native and planted rubber trees present in the backyards. However, there are two large planted rubber plantations called Terra Rica and Ponte where the population has aroused interest in producing natural rubber, but they are abandoned. Thus, the need arose to investigate the feasibility of the revitalization of the rubber trees in order to restructure the activity, making the extraction of the latex a working alternative to the traditional population. In this context, the objective of this research was to evaluate the silvicultural situation, the growth, the production and to carry out an economic analysis of the production of latex and natural rubber. In order to evaluate the silvicultural situation and the growth, two forest inventories were used in 100% of the rubber groves, carried out in 2013 and 2018, and a sampling to investigate the relationship of dendrometric, morphometric and competition indices with growth in diameter, where Pearson correlation analysis (r) was used to verify the existence of correlation. 2.965 rubber trees were inventoried in 2013 and 2,927 in 2018, with a density of 97.9 individuals.ha-1 and 96.6 individuals.ha-1, respectively. The t test detected a significant difference in total height and height of the bole of rubber trees between the inventories of 2013 and 2018, but in diameter, the rubber trees remained the same and, in general, in general, there were no problems of plant health in the plantations. The correlation between the dendrometric, morphometric and competition indices showed that growth in diameter has moderate and weak correlations with all variables, but it presents a significant correlation with the degree of slenderness and salience index. It was concluded that the dendrometric, silvicultural characteristics and growth in diameter of Hevea guianensis have been influenced by the absence of intervention in planting. To evaluate the production of latex and natural rubber, the production of rubber trees was analyzed by means of a sample of 105 young and adult trees, in all diametric classes, during the harvest season in the region. The average productivity per diameter class and the monthly production were evaluated. It was also investigated the existence of possible influences in the production: diameter at 1.30 m from the soil (DBH), bark thickness, crown form and sociological position. Through (r) the correlation of these variables with the production was calculated and the modeling of the latex and natural rubber production (Y) was calculated as a function of the variable of higher correlation (X). It was concluded that the latex production increases with the increase of the diameter of the rubber trees and the production presents seasonal variation, being greater in the period of greater record of rains in the year. As for the influences on the production of latex and natural rubber, these correlated positively and significantly with the DAP and the Sinusoidal and Reciprocal Logarithm models were selected to estimate the production of latex and natural rubber, respectively.