Relação entre hidrologia e assembleia de palmeiras ao longo de gradientesaAmbientais na ESEC Cuniã (interflúvio Purus-Madeira)

Abstract

The relationship between environmental gradients and the set of palms trees (Arecaceae) was investigated in 48 permanent plots installed in 25 km2 of the forest in a fragment between the rivers Purus-Madeira in the Estação Ecologica do Cuniã (Ecological Station Cuniã - ESEC Cu-niã) which is located in the North of the province of Rondônia, Porto Velho municipality. 48 investigated plots, 30 are from the mainland and follow the curve of the ground level to mini-mize the internal variation in soils and topography and 18 plots are riparian and follow the course of streams. For the study of the relationship between the set of palm trees and environ-mental variations, data of surface soil samples were collected and granulometric analysis were made (percentages of silt, sand and clay), macro and micronutrients (pH, Ca, Mg, P, K, Fe, MN, Zn). The local hydrological conditions were measured by the distance of the nearest streams and vertical drainage gradient was measured by the depth of the water table sheet. The depth of the litter was measured every two meters along the centerline of each plot. The structure and floristic composition of the palm trees and the factors related to it was evaluated. The relation-ship between palm trees and gradient of soil, topography, elevation and depth of the local litter were studied, evaluating the most important factors for palm trees forest of canopy and subcan-opy and how small-scale variations change the response of species to environmental conditions. The community showed positive correlation with variable content of silt, phosphorus, sum of bases and distance of the stream, showing that species replacement is linked to local conditions. The study of the relationship between the palms and the hydrologic gradient was evaluated based on the monitoring of the water table, water distance and how species behave according to the variations of the local water conditions. Water is an important factor for the colonization of species of palm trees and affects them differently, based on the size of the species. Finally, it was evaluated how the palm trees set responds to the temporal variation by the analysis of mortality rates and the repopulation of the species. The main gradients related to mortality of palm trees in the area were elevation, and water distance. The repopulation was strongly influ-enced by the content of silt and the water distance.