Estrutura fitossociológica e composição mineral de espécies lenhosas de um fragmento de Caatinga no Semiárido Paraibano.

Abstract

The nutritional composition of the species belonging to the Caatinga biome is little known. Anthropic actions have been contributing to intense change in the areas where vegetations are, leaving only a few areas which have been preserved for a long time. Vegetation in forest ecosystems has a fundamental role in the maintenance of soil fertility, through nutrient cycling. Taking into account the lack of studies on nutritional composition of floristic species of the Caatinga, the aim of this current work was to evaluate the nutritional status of ten tree species with the highest Index Value of Importance (IVI) amongst the caatinga vegetation, in order to provide information on nutritional demands of the studied species in a Caatinga fragment in the semiarid of Paraiba, using systematic sampling method with equal-sized plots of 20 x 20m in which all trees, dead or alive with DBH (diameter at breast height 1,30m up ground) larger or equal to 6cm, were taken into account. In each plot, a composite sample of soil was collected, originated from five simple samples. The samples were collected (0 – 30 cm of depth) for analyses of chemical and textural properties. Foliar material collection for nutritional analyses was carried out in April 2011, in the rainy season, after selection of ten species with the highest Index Value of Importance (IVI). Regarding the collection, four replications with five simple samples each were carried out, totaling ten composite samples in each replication, resulting in forty samples originated from the selected species. After samples preparation, macronutrients and micronutrients analyses were performed. The ten species with the highest value of importance in ascending order were: catingueira (Poincianella pyramidalis), quince tree (Croton sonderianus), mororó (Bauhinia cheilantha), Pereiro (Aspidosperma pyrifolium), Angico (Anadenanthera colubrina), Jurema branca (Piptadenia stipulacea), Imburana de cambão (Commiphora leptophloeos), mofumbo (Combretum sp), Jurema preta (Mimosa tenuiflora), Cumaru (Amburana cearensis). The concentrations of macronutrient and micronutrient contents in the leaves of the ten species with the highest value of importance (IVI) have the following ascending order, respectively: N>Ca>K>Mg>P>S> and Na>Mn>Fe>Zn>Cu>B. The species Anadenanthera colubrina and Aspidosperma pyrifolium shown to be Na accumulator in their leaves, which may be an indication for future works in salinized environments in the Brazilian semiarid.