Nutrients in the litter of a seasonal deciduous forest fragment of Itaara, RS

Abstract

O presente estudo teve por objetivo quantificar a massa e o estoque de nutrientes da serapilheira sobre o solo em um fragmento de Floresta Estacional Decidual no munic\uedpio de Itaara, RS. Para a quantifica\ue7\ue3o da serapilheira, a amostragem foi realizada conforme fra\ue7\uf5es estabelecidas em metodologias: uma para folhas e galhos com di\ue2metro menor a 1 cm (S0) e outra para material lenhoso com di\ue2metro de 1 cm a 3 cm (S1), 3,1 cm a 6 cm (S2) e maior que 6 cm (S3). Para a avalia\ue7\ue3o da fra\ue7\ue3o S0, foram coletadas aleatoriamente cinquenta amostras com moldura met\ue1lica de 25 cm x 25 cm, j\ue1 para a avalia\ue7\ue3o das fra\ue7\uf5es S1, S2 e S3, foram distribu\ueddas aleatoriamente dez parcelas de 3 m x 2 m na \ue1rea de estudo. O material amostrado foi acondicionado e levado ao Laborat\uf3rio de Ecologia Florestal da Universidade Federal de Santa Maria onde foram secas, pesadas, mo\ueddas e analisadas quanto aos teores de macro e micronutrientes. Cerca de 45% da serapilheira depositada sobre o solo \ue9 formada por materiais lenhosos senescentes (galhos e troncos). As fra\ue7\uf5es da serapilheira diferiram significativamente (p < 0,05), quanto aos teores de nutrientes, com exce\ue7\ue3o de Mg e Cu; geralmente a fra\ue7\ue3o S0 apresentou teores mais altos de nutrientes. As fra\ue7\uf5es S1, S2 e S3 apresentaram um ac\ufamulo de nutrientes variando de 53,3% para o K a 8,7% para o Fe em rela\ue7\ue3o ao total da serapilheira, demonstrando a import\ue2ncia da quantifica\ue7\ue3o desses componentes durante a avalia\ue7\ue3o do estoque de nutrientes contidos na serapilheira de ecossistema florestal.The aim of the present study was to quantity aboveground mass and nutrients in a deciduous seasonal forest fragment in the district of Itaara, RS, Brazil. For quantification and fractionation of the litter, sampling was carried out using two methodologies: the first one for leaves and branches with diameter smaller than 1 cm (S0) and the second one for woody material with diameter varying from 1 cm to 3 cm (S1), 3.1 cm to 6 cm (S2), and greater than 6 cm (S3). To evaluate the S0 fraction, 50 randomly sample were collected with a metallic frame of 25 cm x 25 cm, and for S1, S2 and S3 10 plots of 3 m x 2 m were distributed randomly in the area of study. Samples was packed and taken to the Laboratory of Forest Ecology of the Universidade Federal de Santa Maria, where they were dried, weighed, ground and analyzed for nutrient contents. The woody senescent litter represented about 45% of the litter layer. Litter classes differed statistically in relation to nutrient content (p < 0.05), except for Mg and Cu; usually the S0 fraction presented higher contents. The fractions S1, S2 and S3 showed an accumulation of nutrients ranging from 53.3% to 8.7% K for Fe in the total litter, demonstrating the importance of quantification of these components during the evaluation of nutrient stocks contained in the litter of the forest ecosystem