Seria a diversidade biológica apenas uma questão de esforço amostral?

Abstract

The Paulo César Vinha State Park (PEPCV) comprises the coastal salt marsh ecosystem and encompasses preserved original vegetation areas and areas under regeneration after anthropogenic disturbances done after the Park creation. This study aimed to characterize the open herbaceous and shrubby vegetation type in an area not affected by sand mining to (1) evaluate the effect of sampling effort on the diversity of plant species, (2) to compare the values obtained with data available for areas that suffered human disturbance, and (3) generate information for better assessment of the condition of plant community in the areas under regeneration. We installed 50 plots of 10 x 10 m and sampled all shrubs and herbaceous individuals with stem diameter at ground level equal to or greater than 1.5 cm. In total 4,264 individuals were recorded. The sampling effort indicated a multimodal accumulation of richness in plant species, still showing an upward trend of the biological richness without evidence trends to differentiate the local richness of the plots. The Whittaker Richness index was 6.94, the diversity index (H') was 2.95 nat.ind-1 and the evenness (J) was 0.73. The diversity index (H') was lower than in contiguous plots sampled in previous studies and the species richness was also lower in present study. The data available so far suggest that abandoned sand mine pits can promote a different microclimate resulting in increased diversity due to the presence of typical or more common species to other coastal salt marsh formations. Our results demonstrate that the diversity indices are influenced by the sampling effort, although other factors such as the place of sample plots installation and the occurrence of anthropogenic disturbance, although historical, may also contribute to changes in biodiversity values.