Acumulação e decomposição da serapilheira e distribuição de organismos edáficos em área de caatinga na Paraíba, Brasil

• Autor(a) principal: Souto, Patrícia Carneiro
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/8199
• topic: Decomposição da serapilheira; Litter decomposition; Composição química da serapilheira; Respiração edáfica; Caatinga; Mesofauna do solo; Litter chemical composition; Edaphyc respiration; Caatinga; Soil mesofauna; CIENCIAS AGRARIAS::AGRONOMIA

Nutrient cycling is fundamental to forest maintenance, and involves the deposition of organic material, its decomposition and nutrient release for reabsorption by superior plants. These processes are regulated by biotic and abiotic factors that determine the environmental sustainability. This study had the objectives to determine the monthly litter production and the time necessary to the accumulated litter to disappear, characterize the process of decomposition, evaluate the microbial activity and the effect of climatic and soil conditions on it, determine the fluctuations of the microorganisms and mesofauna communities in a Caatinga forest site, and, finally, analyze liter quality in order to identify the different phases of the process of organic matter decomposition and nutrient enrichment. Field work was carried out at the RPPN of the Fazenda Tamanduá, located in Santa Terezinha (PB), from October 2003 to September 2004 (period 1 = P1) and from October 2004 to September 2005 (period 2 = P2) in seven transects systematically located in the RPPN area. Litter production were estimated from monthly litter collection from 20 1mx1m collector boxes randomly distributes in the transects. The collected litter was fractioned into leaves, stems, reproductive structures and miscellany, and then dried and weighed. Every three months the deposited litter on the soil was collected from 0,5mx0,5m frames, dried and weighed, to calculate the decomposition factor (K) and the time required to 50 and 95% of litter decomposition. The rate of litter decomposition was estimated in nylon bags with 30g of dried litter. These 480 nylon bags were divided equitably and placed around the 20 collector boxes. Every month, one nylon bag from each collector bag was recovered from the field and the litter inside was taken out, cleaned and weighed to determine its weight loss. Diurnal and nocturnal microbial activity was measured by means of soil respiration. Macronutrients composition of the deposited litter and in the litter inside the nylon bag was determined. Litter production during P1 and P2 was 1290.9 kg ha-1 and 1947.5 kg ha-1, respectively, totaling 3238.5 kg ha-1. Leaf, stem, reproductive structure and miscellany fractions corresponded to 64.14, 23.48, 10.9 and 1.46% of total litter production, respectively. More litter deposition was observed in the beginning of the dry season. The values of the coefficient of litter decomposition were 1.1 and 1.4 for P1 and P2, respectively, and mean a fast nutrient transfer from litter to soil. The time required to 50 and 95% litter decomposition was 229.9 and 996.4 days, respectively, in P1, and 178.8 and 770.1 days, respectively, in P2. Initial litter weight loss in nylon bags was fast due to the degradation of labile composts by microorganisms, and decreased afterward due to the more resistant and more lignified materials of the remaining litter. Fungi population was larger than the bacteria population, favored by soil water availability. Mesofauna was mainly represented by Diptera’s 67.24% of the total number of counted mesofauna individuals or of the total biomass of mesofauna individuals and Acarine’s (53.49%), in P1 and P2, respectively. The low values of Shannon (0.38) and Pielou (0.15) indexes denoted the distribution heterogeneity of the mesofauna representatives. The order of macronutrient concentrations in the accumulated litter was as follow: N > Ca > S > K > Mg > P. Litter P content was higher than the expected for dry tropical forests.