Função Ecológica de Espécies Arbóreas (Vismia guianensis (Aubl.) Choisy, Inga edulis Mart. e Inga sp.) na Sucessão Vegetal em Áreas Degradadas pela Exploração Petrolífera, na região de Urucu (AM)

Abstract

It was studied the dynamics of natural regeneration beneath the following tree species planted in artificial gaps opened by oil prospecting activities at Urucu’s Base Coari-Amazonas, Brazil (04o53’S and 65o11’W): Inga edulis, Inga sp., Vismia guianensis. The sample plots were set up beneath individual tree canopy (40 for Inga edulis and Inga sp. and 45 for Vismia guianensis) in gaps of three different ages (3, 4 and 10 years old gaps) with three replicates. This study lasted 11 months, covering dry and wet seasons. The seedling species’ distribution was correlated to environmental variables by using the Detrended Canonical Correspondence Analysis (DCCA). The most representative families were: Leg. Mimosoideae (11 genera); Melastomataceae and Myrtaceae (5 genera) and Leg. Caesalpinaceae and Apocynaceae (4 genera each). The species richness beneath Inga edulis, Inga sp. and Vismia guianensis’ trees were greater in old gaps than younger ones. It was also observed a decreasing in species richness from rainy to drier season. Inga edulis and Inga sp. showed higher density and species richness of seedling regenerating under its canopy. Four years old gaps showed the highest seedling density. Inga edulis and Inga sp. showed highest seedling survival rates and species number after 11 months-study. These rates increased with ages. Old gaps showed greater species’ richness, however lower density and lower recruitment rates. Thus, Inga edulis and Inga sp. presented greater coexistence of established species sharing the same primary resources available. Monte Carlo test did not show any significance for Inga edulis + Inga sp., therefore it was impossible to separate colonizer species along the environmental traits axes. In the colonization beneath Vismia guianensis trees, four large groups were visualized (species correlating to environmental factor axes). This indicated the coexistence of seedling species, thus niche partitioning. The highest irradiance and water deficit were the most important limiting factor for seedling establishment and development. Inga edulis and Inga sp. trees presented the best condition for natural regeneration (increased soil organic matter, shadiest canopy, and greater nitrogen content).