Floristic Classification of Large-Scale Ecological Groups in the Forests of Central Zagros

Do climatic variations and drought magnitude affect large-scale vegetation composition in the Central Zagrosian forests, and to what extent do topographic variables of altitude and aspect play a role in these potential differences? To answer this question, in this research, the flora list of 15 Central Zagros forests was obtained in five plant life forms between the valleys of two rivers, Gerdbisheh and Bazeft, over the distance of 170 km, using 226 half-hectare sample plots. Two-way cluster analysis and multi-reference permutation procedures (MRPP) were used to validate significant differences in plant composition at the landscape level. Subsequently, plant communities were divided into three ecological groups: eastern, central and western. Canonical correspondence analysis (CCA) was used to determine the correlation between changing plant composition and climatic and topographic variables as well as plant life forms. The results showed that forests in the western ecological group are significantly and positively correlated with the De Marton aridity index, while the drought magnitude differentiates the other two ecological groups. Also, altitude had a significant effect on differentiating the eastern and central ecological groups. The main difference between the three ecological groups in terms of plant life forms, was due to the significant correlation of Therophytes, Cryptophytes and Hemicryptophytes with the driest ecological group (eastern). Despite the fact that all the plots were covered with forests, Phanerophytes were not effective in distinguishing ecological groups.