Decomposição da celulose da serrapilheira em área de caatinga.

Abstract

Litter decomposition is the main source of nutrients in the soil, and it is of great importance for the sustainability of the vegetation, specially on poor soils. To evaluate cellulose and litter decomposition, litterbags were distributed over the experimental area divided in randomized blocks, in a 8 x 4 x 2 factorial arrangement. The litterbags were buried at four depths ( 0,0; 2,5; 10,0 and 20,0 cm). Samples fforn the litterbags were collected monthly, and analyses were performed to determine N, P, K, Ca, Mg and S contents. Soil respiration was evaluated three times during the experimental period. In these occasions, the C02 liberated from a known area of soil was absorbed by a solution of KOH (0,5 N). This C02 was quantifíed by backtitration with HC1 (0,1 N). It was observed that cellulose and litter decomposition was quite depressed due to the low precipitation registered during the experimental period.N P, K, Ca and Mg were released concomitantly with litter decomposition. Only sulphur concentration showed practically no differences up to 20 cm deep in the soil. The soil respiration method showed to be very useful to evaluate the biodynamics of the soil, that allowed to obtain an idea of the nutrient cycling model in the Caatinga ecosystem. Due to the simplicity of the method and its low cost, we recommend its use.