Plant ecological groups in relation to environmental factors, Ghlarang's forests, Ilam province

The aim of this study was to determine plant ecological species groups related to environmental factors and to specify sites as ecological groups. The study area is located in the Ghelarang's protected area of Ilam in western Iran. In this research, sampling plot size was determined 400 m2 (20×20 m) for inventorying woody species (tree, shrub and bush) and Whittaker’s nested plot sampling was used to survey herbaceous species and minimal plot area was obtained 64 m2. In total, 50 sampling plots were taken using random-systematic method. The coverage percent of woody species were measured in regard to large and small canopy diameter in each plot. The herbaceous species were coded and their coverage percent was estimated. In addition, topographical factors and some physical and chemical properties of soil were taken in each plot. For data analyzing, multivariate methods (i.e., PCA and CCA) were used. Results indicated that 4 trees, 3 shrubs, 1 bush and 78 herbaceous species belonging to 73 genera and 32 families grow in the studied area. Five ecological species groups (i.e., five sites) were recognized according to multivariate analysis. The environmental factors of elevation, organic matter, N, P, K, bulk density, SP, C/N, pH, and clay percent were the most important factors in separating ecological species groups.