Regeneração natural em uma área de campo de agricultura abandonada em ambiente semi-árido

Abstract

Tropical dry forests have been intensively disturbed, however knowledge of their regenerating processes is still restrict. The aim of this study is to evaluate if 16 years of regeneration in an area which the agriculture was descontinued are sufficient for the regeneration of structural and floristic features of an abondoned agricultural field and if the time of abandonment, the precipitation and the distance from a preserved fragment influence the regeneration of this area in Caruaru, PE, Brazil. All individuals with diameter ≥ 3 cm a level of soil were marked and had the height and diameter measured. Structure and floristic data were compared with secondary data of the forest fragment and of other regenerating areas of dry forest, and also to test the influence of the fragment upon the regeneration of the abandoned field. The population dynamics of aroeira, braúna and catingueira were evaluated in 105 plots (5 X 5 m) during two years. All individuals of these three species within the plots were counted and marked; the plots were monitored mensaly to record births and deaths. The field presented lower density, basal area and number of species than the forest fragment; however the number of families and the diversity were similar. Species composition and population density in altered areas of caatinga were more influenced by the precipitation than by the time of abandonment. The density, mean height and maximum diameter of individuals within the plots were not related to the distance from the forest, except for some species. The distance from the forest influenced the number of births and the density of aroeira and braúna, but it was not true for catingueira. The number of births and deaths and the population density varied between years. The total density of the area is one of the parameters of faster recuperation, whereas the basal area and the composition of species are slower ones. The results indicated that 16 years of abandonment were not sufficient for the regeneration of area. Role of preserved fragment on regeneration of antropized area influenced the species differently and this relation is stronger in M. urundeuva and S. brasiliensis. Annual variation in demography of tre species may be related to variations on rainfall. This study confirms the importance of forest fragments in the regeneration of altered areas, and suggests the importance of their preservation.