Leaf breakdown and N, P and K release rates of Caatinga species

O objetivo da pesquisa foi avaliar a influencia da temperatura e umidade edaficas e da composicao quimica sobre as taxas de perda de massa e liberacao de nutrientes da fracao foliar de algumas especies endemicas do Curimatau paraibano. Simultaneamente as coletas mensais do material remanescente acondicionado em sacolas de nailon, foi mensurada a temperatura na superficie edafica e retiradas amostras de solo para determinacao do seu conteudo de umidade. Os teores em N, P e K, nos residuos, foram comparados com a concentracao desses nutrientes nas amostras iniciais, as quais tiveram seus teores de carbono, celulose, hemicelulose e lignina e as relacoes C/N, Lig/N e P/Lig utilizados como preditores das taxas de decomposicao dos tratamentos. Observaram-se variacoes nas taxas de decomposicao entre as diferentes especies e maior perda de massa no periodo chuvoso. Os parâmetros quimicos utilizados nao foram suficientes para explicar as taxas de decomposicao de todas as especies. P e K apresentaram correlacao com a efetiva perda de massa dos tratamentos. K foi o nutriente de liberacao mais rapida da serrapilheira foliar, enquanto N apresentou acumulacao para a maioria das especies. Abstract The objective of this study was to evaluate the influence of temperature and soil moisture and chemical composition on rates of mass loss and nutrient release of leaf fraction of some endemic species in Paraiba Curimatau. Simultaneously with monthly gathering of the remaining material placed inside nylon bags was measured edaphic surface temperature and soil samples for determination of content moisture. The amounts of N, P and K in residues were compared with the concentration of these nutrients in initial samples, which had its carbon content, cellulose, hemicellulose, and lignin and the relationship C/N, Lig/N and P/Lig utilized as treatment decomposition predicting rates. They were observed variations in decomposition rates between different species and increased mass loss during the rainy season. Chemical parameters used were not sufficient to explain the decomposition rates of all species. P and K presented correlation with treatments mass effective loss. K was the nutrient with faster release leaf litter, while N presented accumulation to majority species.