vegetation-environmental relationships and ecological species groups of the ilam oak forest landscape, iran

the study was carried out in the ilam oak forest that is located in the west part of iran. the objective of this research was to determine the plant ecological groups and site classification in this region. data were collected from 117 sample plots using the systematic-random sampling method. the size of sampling plots was 20 m?20 m for the tree and shrub species and 1.5 m ?1.5 m for herbaceous species. whittaker?s nested plot method was used in order to record the herbaceous species. soil samples were collected and analyzed to study soil properties. multivariate analysis methods were used to classify and determine the relationship between species composition and environmental factors and to recognize ecological species groups. pc-ord and spss software were used for data analyzing. five ecological groups were specified in the study area. cerasus microcarpa was the indicator species in the first group, which showed high correlation with carbon and nitrogen. quercus brantii showed the strongest correlation with caco3. the third group was acer monspessulanum. elevation and clay were the most important factors that separated this group. amygdalus orientalis showed high correlation with elevation. these two above mentioned groups were located in higher altitude. astragalus liyciodes was the indicator species in another distinct group in the study region with high level of stoniness percentage. astragalus group was observed where soil stoniness was high. results also showed that groups at higher elevation showed lower richness.