Dams consequences to the woody regeneration layer of dry forests

Resumen

Local changes caused by dams have drastic consequences on ecosystems, however, studies assessing temporal changes on the regeneration layer after these disturbances are rare. Thus, the consequences of the water line closeness to the regeneration layer of two seasonal dry forests, a deciduous dry forest and a semideciduous dry forest, on southeastern Brazil were evaluated. These forests have a severe dry season on winter and many plant species are deciduousness and disperse their seeds by wind, two mechanisms used to reduce the negative effects of the dry season. However, with the waterline closeness, the dry season can be smoothed and species with other traits should colonize this environment in detriment of the typical dry forest species. Then, one points out the hypothesis that several changes may have occurred in the regeneration layer just three years after damming, such as an increase in richness and the establishment of evergreen and zoochoric species, because the damming increased the water supply to the community. Thus, 40 plots of 5 x 5 m were distributed close to the dam margin and all plants with circumference below 15 cm were cataloged before and three years after damming. Two plant traits were also evaluated: (i) the deciduousness and (ii) dispersion syndrome of all species. The results show an expressive increase in number of individuals of plants on both forests, along with increase in richness, mainly zoochoric and evergreen species. Closeness to water probably relieved the effects of the dry period common in seasonal environments, allowing new trees and different species to establish themselves on the forests.