Journal of Rangeland

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This study aimed to investigate the effects of topographic, climatic and soil factors on the distribution of Agropyron libanoticum in the upstream rangelands of Amirkabir dam in Alborz province. We collected the environmental and vegetation data from 35 sites in the study area. In each site, 10 one square meter plot placed along a 100-meter transect, and the presence or absence of species was recorded. Moreover, canopy cover and density of other species, soil depth, stone and gravels percentage, and total canopy cover were recorded. Thirty-five soil samples from 0-30 cm of the soil surface were collected and their texture, phosphorus and organic matter contents were measured in a soil laboratory. Digital elevation model was derived from the topographic maps, and the elevation, slope, aspect maps were produced accordingly. Rainfall and temperature maps were produced using available data and their values for the studied sites were extracted. The independent T-test was used to compare sites with the presence or absence of the species. Cluster analysis was performed to grouping the sites based on environmental factors. Discriminant analysis was used to determine the importance of environmental variables on A. libanoticum distribution. Results revealed that elevation, rainfall, average temperature, stone, and gravel percentage, and organic matter varied significantly between the presence and absence sites of the species (P < 0.05). According to the cluster analysis, A. libanoticum prefers habitats with an altitude of 1850 to 2600 m, rainfall of 500 to 680 mm and mean annual temperature of 7 to 11 ̊ C. Agropyron libanoticum is more abundant in soils with moderate texture, low depth, and high gravel percentage. Soil with 0.5 to 1 percent organic matter and 3.5 to 5.5 ppm phosphorus contents provides more appropriate conditions for the growth of this species. The results of the discriminant analysis showed that rainfall, elevation, temperature, slope, soil texture (sand, loam and clay content), aspect, gravel percentage, phosphorus, soil depth, total canopy cover, and organic matter are the most important factors in the distribution of A. libanoticum in the study area. According to the results, this species is an appropriate species in restoration and reclamation programs of mountainous rangelands with steep slopes and low depth soils.
 

Keywords: Ecological factors, Habitats factors, Agropyron libanoticum Hack. ex Kneuck., Amirkabir dam rangelands, Alborz province.

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