Avaliação populacional de Sesbania virgata (Cav.) Pers. (Fabaceae Lindl.), nas margens do rio Paraíba

Abstract

The species Sesbania virgata (Cav.) Pers. was virtually unknown in the ecosystems of the Paraiba state until up to two decades ago, when it began to occupy riverbanks and margins of the artificial water reservoirs, revealing itself as an invasive species of certain niches. This work was carried out in a stretch of the Paraíba River, downstream of the Argemiro de Figueiredo dam in the municipality of Natuba, Paraíba, Brazil, in February 2009. This study was undertaken to evaluate the populacional structure of this specie, the production and allocation capacity of photoassimilates to different parts of the plant. Ten parcels of 5 × 5 m (25 m2) were plotted and all S. virgata individuals inside them were counted. Randomly, 20 adult specimens were selected, and their height, diameter at ground level, and crown diameter were measured. After the measurement, these individuals were cut at ground level, sub-divided, put into bags and taken to the Laboratory of Plant Ecology, CCA, UFPB, Areia, where the material was separated into different parts such as unripe fruits, ripe fruits, branches and leaves. Each sample of these materials was weighed (green biomass), and placed in a forced air circulation stove at a temperature of 65°C until constant weight, when the dry biomass was determined. S. virgata has a high fruit production, which is an invasion strategy. The species S. virgata is an aggressive weed in the studied environment, with high population density.