The influence of the micro spatial heterogeneity in the diversity of herb plants was evaluated in a caatinga site at Caruaru, Pernambuco, Brazil. Three microhabitats were chosen: a flat area with a rocky yellow podzolic soil, a similar area with the same soil type but without rocks and an area at the border of a small intermittent stream but that is never covered by floods. In each microhabitat, 35 plots, 1m² each, were marked, at random, and all herb plants identified and counted. Plants were also collected and identified in the same microhabitats outside the plots. A total of 62 species were found in the three microsites, 32 in the flat area, 42 in the rocky area and 39 in the stream area. Similarity, using Jaccard index, ranged from 42% (flat x stream area) to 57% (flat and rocky area). The sampled plots in each microhabitat contained 1749, 1020 and 1240 herb plants, respectively, with species richness of 3.09, 3.88 and 4.18 species.(ln plants)-1 and Shannon-Wiener diversity indices of 2.08, 2.09 and 2.52 nats.plant-1. Malvaceae, Euphorbiaceae and Poaceae were the families with highest number of species. About 19% of the species were climbing plants and were considered an important group for local biodiversity conservation. The importance of the inclusion of the herb plants of the different microhabitats for the determination of the floristic richness of the caatinga was confirmed.
species richness; herb density; semi-arid; caatinga; microsites
