A comunidade de pequenos mamíferos e o processo de regeneração de palmeiras em fragmentos florestais isolados por água na amazônia central

Abstract

Due to high deforestation rates that currently are occuring in tropical environments, it is necessary to understand how biological communities are being affected by the changes in landscape configuration. The study of relationships between ecological attributes and the spatial patterns of landscape configuration lead to the development of the Landscape Ecology, an essential issue in the study of forest fragmentation. Twenty years after the construction of Balbina’s dam in the Uatumã river, Central Amazonia, the majority of biota that survived from flooding are isolated in islands from different sizes and isolation degree. In this context, the purposes of this study were assess how the small mammal community dynamics are affected by the changes of landscape configuration due to the flooding process, through the analysis of patches size and isolation degree. The relationship between dynamics of the small mammal community and the regeneration process of the palm community were also studied. The small mammal community was sampled between July and December of 2006 with live traps (Sherman and Tomahawk) in 12 study sites (8 islands and 4 sites in continuous forest). In total, 110 individuals of small mammals were captured, belonged to 13 species and three families (Didelphidae, Muridae and Echimyidae). The total effort in Balbina was 9600 traps night. The palms were sampled in 100 X 1 m plots at the same sites where small mammals were sampled. A total of 630 palm individuals, belonged to 11 genera, were recorded in the study area. The decrease of isolation degree affected positively the occurrence probability and the abundance of Monodelphis brevicaudata, total abundance and richness of small mammals and the palm diversity in islands, but negatively affected the abundance and occurrence probability of Didelphis marsupialis. Monodelphis brevicaudata had a greater occurrence probability in larger islands, although total abundance and richness of small mammals were lower in those islands. Palm diversity in islands was negatively correlated with the abundance of Micoureus demerarae, Proechimys guyannensis and Proechimys cuvieri. We concluded that both isolation and size are important attributes for the observed changes in the structure of small mammal and palm communities in Balbina. Smaller and highly isolated islands are prone to a small mammal hyper-population phenomenon. We highlighted the importance of testing new hypotheses related to other landscapes and environmental factors that may influence the studied communities as research priorities for future studies in Balbina.