Fitossociologia para caracterização de estado de conservação de fragmento florestal urbano

Abstract

Due to deforestation, Cerrado biome vegetation is fragmented, forming mosaics of vegetation in what was previously a massif. Part of these fragments are located in urban areas and suffer disturbances imposed by this matrix. In Cuiabá-MT, some of them have been surveyed aiming conservation of the remaining vegetation. Among them is the study area of the present work, located within the State Secretariat of Environment of Mato Grosso (SEMA-MT). Based on a census of arboreal/shrubby individuals with DBH ≥ 5 cm, the floristic composition survey and the analysis of Google Earth Pro images, floristic study was carried out for species ecophysiological groups classification (pioneer - PI; early secondary - SI; late secondary - ST; climax - CL) and fruit dispersal syndromes (anemochoric - ANE; autochoric - AUTO; and zoochoric - ZOO); the study of the horizontal structure, through the phytosociological parameters of density, dominance and cover value, and diametric distribution; the study of the vertical structure, through the social position of the species; as well, the evaluation of the vegetation suppression over time and the isolation of the area, by satellite images. It was observed that most species (50 spp. and 41 spp., respectively) are anemocoric and zoocoric, and that the dispersing agents of the latter syndrome are mainly birds and bats. Species ecophysiological groups classification resulted in, 24 pioneer species and 28 are early secondary. The species with the highest CV (18,04%) was Protium heptaphyllum, which has zoochoric dispersal by birds, with more than twice as many individuals as the second species with the highest CV in the area. The horizontal structure follows a "reverse-J shapped" diametric distribution and the species were concentrated in the middle and upper stratum of the community, in which P. heptaphyllum had the highest social position (21.97%). Significant area reductions were imposed in the fragment along urban matrix development without isolation constrains, surrounding areas, within a radius of 1 km, are composed by 9 nearby fragments providing connections with the study area, indicated by a significant amount of ornithocortical and chiropterocortical species. Thus, based on the results, it was possible to conclude that, due to the large number of species of early seral stages and their ecological importance in the structure of the study area, the fragment is disturbed and this is a consequence of constant suppression of vegetation. The low frequency of individuals in the lower stratum of the community indicates that, in the future, the presence of some species will be compromised. But despite this and its location in an urban matrix, the fragment is not isolated, since the large number of species dispersed by birds and bats, P. heptaphyllum being an example of the efficiency of this type of dispersion. Furthermore, it demonstrates how the fragment is essential for the maintenance of wildlife in the urban matrix.