Influência da Exclusão de Água na Produção de liteira em Floresta Primária de Terra-firme, Caxiuanã, Melgaço, Pará

Abstract

Litter represents the major input of organic matter from the above-ground part of the vegetation into the soil; it is composed of leaves, stems, twigs, fruits, flowers, and other plant parts, as well as the remains of some animals and fecal material. This study aims to evaluate the influence of water exclusion in the forest on the primary production of litter and determine the participation of its components (leaf, twig and reproductive). The study was conducted at the Estação Científica Ferreira Penna- ECFPn, Caxiuanã, Pará, a dense terra firme forest. The material was collected monthly from 20 collectors in plots A and B and 18 in plot T and was dried, sorted and weighed. The estimated total primary production of litter was different in plots (A, B and T), with the following values: 13361.66 g/m'; 11410.24 g/m'; 12565.84 g/m' for the year 2004 and 13009.99 g/m'; 9808.98 g/m'; 11392.57 g/m' for 2005; the lowest production occurred in plot B. The leaf fraction has approximately 72 % participation within the total litter production; 13.91 to 16 % of gravets and 12.02 to 14.88 % of reproductive. There was no variation in litterfall between plots, however, there was a reduction in the reproductive fraction (flowers, fruits, seeds) in the area (B) that suffered water exclusion, producing 957.67 g/m' and 856.01 g/m' in the corresponding years and also, in this area, there was a difference in leaf production. The production of litter was influenced by the seasons (dry, wet, dry-humid and wet-dry transitions), being the dry period, corresponding to the month of July to October the one that presented the highest production; with a value of 11837.7 g/m' in 2004 and 14502.97 g/m' in the following year. The forest of Caxiuanã presents seasonality in the fall of litter, which is characteristic of dense dryland forest of the Brazilian Amazon, because it showed greater deposition of litter in the dry season; being a tropical forest, it had continuous production of litter throughout the year. The exclusion of water in the forest has an effect on litterfall, having a strong influence on the reduction of the reproductive fraction.