Plant communities change under different physiographic conditions and soil properties in the central Zagros forests

Different physiographic conditions and soil properties have resulted in the establishment of different plant communities in central Zagros forests. This study aimed to differentiate these plant communities by means of detecting the species similarity and relations between understory plant vegetation, physiographic conditions and soil properties. Sampling was conducted using 21 modified multiscale Whittaker plots that were randomly distributed amongst the vegetation types. In each plot, species name and canopy cover as well as physiographic data were recorded for each individual tree, and soil specimens were sampled. The relationships between understory vegetation and environmental variables were investigated by means of two way indicator species analysis (TWINSPAN) classification method as well as two ordination approaches, including detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA). The results of ANOVA, ordination, and classification in segregation of vegetation types showed that the distribution of vegetation types, species and also ecological species groups in central Zagros is affected by altitude, slope, geographical aspects, and the amount of soil organic C and N. Moreover, the results of vegetation classification segregated local vegetation into three ecological groups, including 12 indicator species. These results were in line with the ordination results. This study showed a high resemblance between the results of vegetation classification and ordination in accordance to the extent of study area (landscape scale) and random selection of sampling units at the physiognomic types and the ecotones.