Changes of morphological traits of Astragalus brachyanus species under environmental and management factors in mountainous rangelands of Rajhan, Urmia

Measuring plant traits is one of the essential requirements for calculating functional diversity indices. Therefore, the present study aimed to investigate the changes of morphological characteristics of Astragalus brachyanus species under the influence of environmental and management factors. In order to measure plant traits, three transects of 50 m long were located in each location. On each transect, five random points were selected and the closest plant base to the random point was identified. Finally, 15 stands per plant were selected to measure plant traits. At each site, three composite soil samples were also taken to measure soil parameters. Some environmental and management factors such as slope, aspect, elevation and grazing intensity of locations were also noted. Data reduction was performed using Principal Component Analysis (PCA). Regarding the calculated gradient length, RDA was used as linear method to study the relationship between vegetation traits and environmental factors. The results showed that the mean traits of crown diameter, collar diameter, base height, branch length and biomass dry weight in A. brachyanus were significantly different among distribution sites. According to the ordination diagram, branch lenght is mostly influenced by the elevation; collar diameter, affected by soil silt percentage and dry weight of biomass is affected by modified azimuth aspect. The height of the stands was affected by the percentage of porosity and crown diameter is affected by the percentage of sand. The results indicate the influence of environmental factors on morphological traits of A. brachyanus.