Structure and spatial distribution pattern of Cyathea delgadii Sternb. (Cyatheaceae) in two Cerrado areas, in the Northeast of Brazil

Abstract

The research analyzed the population structure and spatial distribution pattern of individuals of two populations of Cyathea delgadii Sternb. (Cyatheaceae), occurring in Cerrado areas in the state of Maranhão/Brazil. The study areas are located in the East of Maranhão, in the Milagre village, municipality of Matões and in the Pedras Village in the municipality of São João do Sóter. In each area, seven contiguous plots of 30m x 10m (300m²) with 20m inter distribution between plots. Were sampled in the unitsall the individuals of C. delgadii, with height of the living caudex and diameter at the ground level (DNS). The height of the sampled individuals was distributed in classes and for analysis of the spatial distribution, the Morisita index and the variance/average ratio calculation were used. The statistical significance was verified through theChi-squared. Were sampled 120 and 39 individuals in 100% and 90% of the plots in the Milagre and Pedras Villages, respectively, mostly in the first height classes (> 0-0,8m and> 0,8 - 1,6m). The distribution pattern of the two populations of Cyathea delgadiiwas aggregated with statistical significance. With the results are inferred some biotic and abiotic factors that can influence the distribution of Cyathea delgadiiin its habitat and construction of its population niche. The data presented in the research made it possible to aggregate basic information for the management and preservation of this species in the Brazilian Northeast, contributing to the population knowledge of arborescent ferns.