Tree species composition and diversity of the Morro Grande Forest Reserve, Cotia, SP, Brazil

Abstract

The main objective of this study was to characterize the tree arboreal species composition and to compare secondary and mature forests of the Morro Grande Forest Reserve (Cotia, metropolitan region of São Paulo, Brazil). Based on this evaluation, we discuss the forest type classification and the conservation value of this Reserve. We used the point centered quarter method, sampling 2,400 trees in six different sites, three with secondary forests and three other ones with a predominance of mature forests. In each site, four blocks of 25 points were assessed, totalizing 100 points or 400 individuals. The blocks were 200 m apart from each other. Data were analyzed through cluster and Detrended Correspondence Analysis (DCA). Results showed differences among sites, essentially differentiating the secondary and mature sites. DCA and cluster analyses were particularly useful to detect characteristic species for these two main successsional stages. Among the 260 species observed, only 12 were sampled in the six sites. Richness and diversity were surprisingly high when compared with previous studies in the study region. The Shannon diversity values were among the highest in the state of São Paulo, with 4.75 nats/tree for the whole sampling, 4.25 nats/tree for the three secondary sites, and 4.54 nats/tree for the three mature sites. The studied forest may be essentially classified as "Dense Mountain Rain Forest" presenting species from the Araucaria mixed forest, and also from the semi-deciduous forest and Cerrado (woody savanna) region. Those results seem to confirm the hypothesis of a "high montane refuge" in drier climatic conditions in the past. The high richness and mixed composition of different floras highlighted the importance to preserve the Morro Grande forest.