On the relationship between vegetation cover and physiographic factors in a gallery forest in southern Urmia, NW Iran

This study aimed to 1) investigate the relationship between vegetation cover and physiographic factors and 2) determine the indicator species in ecological groups in a gallery forest of Darreh-Khan river in the south of Urmia, NW Iran. Minimal area method was used to determine the area of sample plots. Based on this, arboreal and herbaceous cover plots were recorded in 400 and 100 m2 plots, respectively. Using the Braun-Blanquet cover-abundance scale, arboreal and herbaceous taxa were recorded respectively in 32 and 50 sample plots centered at 0, 20, 50, 100, and 200 m along transects perpendicular to the river axis on both sides at 200 m intervals. We applied cluster and indicator species analysis in order to determine the ecological groups and indicator species. In addition, non-metric multidimensional scaling (NMS) approach was applied to analyze the relationships between vegetation and physiographic factors in the study area. Cluster analysis divided the herbaceous species into three (north-facing slope, south-facing slope, and near-river) ecological categories. The NMS analysis showed that slope and altitude are among the most influencing environmental variables on the distribution of herbaceous plants in this ecosystem. Examples of the indicator plant species in ecological group I (north-facing slope) included Astragalus persicus, Echinops bithynicus and Silene marschallii, whereas Salvia multicaulis, Onosma sericeum and Aristolochia bottae were amongst the indicator species in ecological group II (south-facing slope). Colchicum szovitsii, Galium spurium and Pimpinella anthriscoides were grouped in the third category (near-river). Moreover, woody taxa were seperated into two ecological groups: near-river (Juglans regia and Pyrus syriaca) and far-from-river (Cerasus microcarpa and Pistacia atlantica).