Floristic aspects of the Itapeva Ecological Station, SP: a protected area in the southern limit of the Cerrado biome

Abstract

The Itapeva Ecological Station - EEcI (24º 04' S and 49º 04' W, altitude 750 m), Itapeva, São Paulo State, is a Protected Area (PA) predominantly covered by cerrado denso and cerradão, whose occurrence in the region represents the southern limit of distribution of cerrado sensu lato. Aiming to know the regional flora and assuming the existence of floristic peculiarities due to the local weather conditions (incidence of frosts and absence of water deficit), we conducted a floristic survey in this PA from February 2008 to May 2010 and recorded 437 species in seven different physiognomies. In the cerrado sensu lato physiognomies, 346 species, distributed among 87 families and 220 genera, were found. The richest families were Asteraceae (31 species), Fabaceae (27), Myrtaceae (26), Melastomataceae (21), Rubiaceae (15), Lauraceae (12), Bignoniaceae (11) and Poaceae (10). Concerning richness and family representativeness, the EEcI flora does not differ from that of other cerrado sensu lato remnants at lower latitudes. However, frequent species in those remnants - Dimorphandra mollis, Xylopia aromatica, Eugenia aurata and Tocoyena formosa - were not found in the study area region, probably due to frost effects and other limiting climatic factors. On the other hand, geographical distribution models did not predict the occurrence of Annona dioica, Brosimum gaudichaudii, Duguetia furfuracea, Anadenanthera peregrina var. falcata, Caryocar brasiliense and Schefflera vinosa for the region of Itapeva, possibly due to the absence of water deficit. The floristic data obtained in this study may assist in the parameterization of these models. The floristic similarity observed between the physiognomic extremes of the cerrado sensu lato in the EEcI: cerradão and cerrado ralo, 26%, was smaller than the floristic similarity between the swamp grassland physiognomy and the cerrado ralo (27%), and between the former and the cerrado denso (30%). Therefore, considering floristic composition as one of the defining aspects of vegetation type, the swamp grassland can be included in the delimitation of cerrado sensu lato in the EEcI. We recorded eight species threatened with extinction. Due to the PA's small dimensions, we suggest the expansion of its area for a more effective conservation of these species' populations.