Padrões e processos agroecológicos no assentamento Benfica, município de Itupiranga, Pará

Abstract

In this study were analyzed the diversity of a agricultural matrix of the Benfica Settlement Project, an area of recent colonization, located in Benfica Settlement Project, Southeastern Pará state, Brazil. The specific objectives were to analyze the floristic structure and composition of the remaining forest, characterize the successional stages through the floristic composition and structure of secondary forests, and describe the effect of the landscape in richness and abundance in habitats. 65 floristic surveys were conducted in different sites (habitat), following a standardized methodology. In each site one 10 x 50 m (500 m2 ) transect were sampled to survey the plants with diameter-at-breast-height, or DBH > 10cm (Upper stratum). A 5 x 50m subplot was allocated in each plot to survey the plants with DBH < 10cm and taller than 2m (Middle stratum), and within of 5 x 50m subtransect another 1 x 50m subtransect was placed to count the herbs and seedlings species less than 2m in height (Lower stratum). The species were classified into five lifeforms: trees, shrubs, vines, palms and herbs. These lifeforms were classified into two functional groups: pioneer and forest species. Eleven sites of remnants forest were analyzed and presented a structure very similar to the primary forests of the region, with a large number of forest species and the majority of woody species in three strata studied, in addition, most herbaceous species found in the lower stratum were typical species of understory of primary forests. However, signs of disturbances can already be seen in a in some sites studied, a fact that indicates a worrying fact for their conservation.The successional process was described based on 22 different sampling sites with aged between one and 20 years, and the remaining forests as control. The secondary forests still suffer strong influence of remaining forests as result of the recent history of land use. The successional stages can not be classified by structural parameters only, the parameters floristic should be considered. The age strongly influenced the young and the remaining forests; however, the history of use strongly influenced the formation of secondary forests that remained for a long period as pasture. To describe the effect of the landscape in richness and abundance in different habitats were used the 65 sites studied. The richness, in general, is strongly linked to exclusive species of each habitat; thus, the different habitats contribute to the conservation of the landscape. The remaining disturbed forests, riparian forest and secondary forests of up to 15 years were those that contributed most to the richness and abundance of most lifeforms, but the crop fields and pastures were also important for herbs and vines. The riparian bush vegetations are among the natural habitats, the most degraded. The lifeforms studied respond differently to the changes of habitat. The trees are strongly linked to the remaining natural habitats such as remaining and riparian forests, the abundance of shrubs in riparian bush vegetation seems to relate with the changes caused by degradation of riparian forest and herbs, lianas and palms seem to respond to the successional process which is established in landscape.