Atividade, carbono e nitrogenio da biomassamicrobiana de solos de terra firme e igapó da Floresta Nacional de Caxiuanã-Pará.

Abstract

According to Jenkinson & Ladd, 1981, the soil microbial biomass is the main responsible for the decomposition of organic residues, the cycling of nutrients and the flow of energy within the soil, exerting its influence on both the transformation of organic matter and the storage of carbon and mineral nutrients. In order to complement the work carried out by LBA and other MPEG projects, this study aims to determine the activity, carbon (C) and nitrogen (N) content of the microbial biomass in soils from terra firme (LBA sites ESECAFLOR and PNOPG plot) and igapó at the Ferreira Penna Scientific Station in Caxiuanã - Pa,. Soil samples were collected during the dry and rainy periods of the region during 1 year at 5 different sites: (1) LBA - Experiment, (2) LBA - Control, (3) PNOPG, (4) Igapó - North and (5) Igapó - South with five repetitions each, at a depth of 0-20 cm. The incubation method was used to determine soil microbial activity, and fumigation-extraction was used to obtain microbial C and N. During the dry season, microbial activity varied from 0.66 to 1.18 cmot.drn+and from 0.53 to 0.73 crnol.drn? during the rainy season. The highest values of microbial activity were found in the dry season, at the LBA- Experiment (1.63 cmol.drrr") and LBA- Control (1.12 cmol.dm+) sites. The Igapó North and South sites presented higher microbial biomass carbon values (1010.60 and 974.36 mg C kg-1 soil, respectively) than the other areas. However, in all areas studied microbial biomass C and N were higher during the dry season. The results suggest that the rapid variations in climate combined with the change in soil moisture interfere with the structure of the soil microbial community due to the occurrence of water stress mainly during the dry season.