Biomassa acima do solo de um ecossistema de "campina" em Roraima, norte da Amazônia brasileira

Abstract

The aboveground biomass of a "campina" ecosystem was estimated in Roraima, in the northern portion of Brazilian Amazonia. The biomass was determined from a phytosociological inventory (1 ha) and distributed between two categories: (1) grassy-woody, composed of "herbs+lichens" (Poaceae, Cyperaceae, Eriocaulaceae, Cladonia spp), Bromeliaceae, seedlings, fine and coarse litter and, (2) woody, composed of trees and bushes. The grassy-woody category was estimated by the direct method (cutting and weighing) in 10 1-m² plots, taking advantage of transects of the inventory. The category woody was estimated by the indirect method cutting 98 individuals of different species and diameters. A model was generated to express the relationship among total dry above-ground biomass (kg), base circumference (cm) and total height (m) for the individuals in this category. The equation was applied to the 3,966 ind.ha-1 observed in the inventory. The total biomass was estimated at 15.91 t.ha-1, of which 2.20 ± 0.23 t.ha-1 (13.8%) was in the grassy-woody category and 13.70 ± 7.13 t.ha-1 (86.2%) in woody category. The tree species with the highest biomass was Humiria balsamifera (Aubl.) St. Hill. (8.43 t.ha-1), followed by Pagamea guianensis Aubl. (1.14 t.ha-1). These results are important for refining the calculations of greenhouse-gas emissions from burning and decomposition of above-ground biomass in "campina" ecosystems in the Amazon region.