Classification of Vegetation and Its Ordination Regaring Geologic, Physiographic and Edaphic Factors (Case Study: Manesht Protected Area, Ilam, Iran)

This research aimed at studying the vegetation and investigating the effects of physiographic, edaphic and geological factors upon distribution of plant communities in Manesht district in Ilam province. Sampling was done based on plant types and land unit map. The number of samples was determined by Krebs method. In total, 125 square sampling plots of 400area were selected by random systematic method. To determine soil factors, two soil samples (0–30, 30-90 cm deep) were collected from each land unit and physico-chemical parameters were measured. Using TWINSPAN, vegetation of study area was classified and then PCA and CCA were used to investigate the relationship between vegetation and environmental factors. Based on TWINSPAN, four vegetation groups were recognized. According to TWINSPAN results, four ecological groups were identified that first and second groups with 31 and 46 sample plots, respectively and by Quercus barantti, Crataegus pontica and Acer monspessulanum, as indicator species, are more calciphiles than another groups. The first three axes of the PCA accounted for 62.83%, 23.45% and 13.72% of the total plant cover variability, respectively. Also based on Mont Carlo analysis, first and second axes with 0.68 and 0.48 eigenvalue, accounted for 28% and 19% of the variability, respectively and the correlation coefficient of axes and species is 0.98. According to PCA and CCA, Formation, organic matter and lime were the most important factors on establishing of ecological groups.