Environmental factors-ecological species group relationships in the Surash lowland-mountain forests in northern Iran.

Identification of the primary factors that influence the ecological distribution of species groups is important to managers of lowland-mountain forests in northern Iran. The aim of this study was to identify main ecological species groups, describe the site conditions associated with these species groups and the relationships between environmental factors and the distribution of ecological species groups using multi-variate analysis (Detrended correspondence analysis (DCA) and Canonical correspondence analysis (CCA)). For this purpose, 50 relevés (400 m² each) were sampled using the Braun-Blanquet method. Vegetation was classified into three ecological species groups using a modified two-way indicator species analysis (TWINSPAN). In each relevé, environmental factors (topographic and soil variables) were measured and analysed using one-way ANOVA and Pearson r statistics. Further, species diversity indices were determined for the identified ecological species groups. Our results show that the environmental factors, e.g. elevation, slope, slope aspect, soil texture, pH and organic matter, were the most important factors explaining the distribution of the three ecological species groups in the study area. The diversity of the ecological species groups decreased with elevation. The results provide an ecological basis for forest management and for developing strategies for forest conservation in the study area. [ABSTRACT FROM AUTHOR]