Aporte e decomposição de serrapilheira em área de caatinga, na Paraíba.

Abstract

Litter contribution and decomposition in a caatinga area, in Paraíba. The present work had as objective to evaluate the deposition and decomposition of the organic material and the microbial activity of the soil. The experiment was carried out between September/2003 and June/2004 in the RPPN at Fazenda Tamanduá, Santa Terezinha (PB), to estimate the litter produced. Twenty collectors measuring 1.0 m x 1.0 m were used, with a nylon mesh bottom at 30.0 cm from the ground. The collected material was separated into fractions, dried in an oven, then weighed to determine the dry biomass. For litter decomposition, the material was packed in 20 cm x 20 cm nylon bags, 1 mm' mesh, with 30 g of litter. The bags were placed on the soil surface and, monthly, a bag was removed from each treatment, in which the decomposition was evaluated by the weighing method. The microbial activity was estimated using 0.5N KOH solutions, in which it absorbs the CO² released from the soil. This solution was then titrated with 0.1N HCl. After ten months of collection, 899.2 kg ha"1 of organic matter were deposited in the caatinga, while 505 kg ha"1 of leaves, 257.4 kg ha"1 of branches, 22.5 kg ha"1 of miscellaneous, 114 .3 kg ha"1 of reproductive structures. The analysis of data interpretation allowed to conclude that the microbial activity was influenced by precipitation, being higher at night; litter deposition was higher after the end of the rainy season, with the leaf fraction contributing with the highest percentage, and the experimental period was not sufficient for the total decomposition of the litter.