Regeneração natural das clareiras antrópicas da Província Petrolífera de Urucu-Coari, AM

Abstract

We studied the environmental variables and species composition in natural regeneration in 10 anthropogenic clearings in the Urucu Petroleum Province (Urucu- Coari/AM). We used the methodology typical of phytosociological surveys, analyzed Soil samples and measured the distance between the clearings and the edge of the forest. We used Canonical Correspondence Analysis (CCA) to examine the relationship between the floristic composition and the environmental variables. All 10 gaps had low diversity and evenness and a larger number of pioneers than the climax species, with a greater concentration of specimens in the lower height classes, and included exotic species. Herbaceous species predominated in gaps 19, 25 and jazida 33 while woody species predominated in jazida 21, jazida 22 and RUCs and LUCs. Some gaps almost completely closed canopy layers with the understory poorly stratified, mainly when the the canopy was dominated by exotic species as Clitoria racemosa and Syzygium jambolanum or there was densgrowth of native species of Inga. According to the CCA, the occurrence of the most frequent species, Bellucia grossularioides, and the most abundant species, Fimbristylis diphylla, are related to lower levels of Al and Ca respectively. The occurrence of the majority of herbs (Poaceae and Cyperaceae) was positively related to Al concentration and the distance between the clearing and edge of the forest, while that of most of woody species were related with moderate levels of Mn. The gaps (19 and 25) are related with herbaceous species while deposits, RUCs and LUCs are more related to woody species. The gaps 19 and 25, deposits, RUCs and LUCs are associated with Al, distance between gap and edge of the forest and low concentrations of Mn. The results indicate that the clearings were in the early stages of ecological succession and that the exotic species S. jambolanum and C. racemosa, and the native species of the Inga, are the main inhibitors of natural regeneration of native species.