Evaluating the effect of geomorphology on the vegetation type and density of Foshtanq alluvial fans, Sabzevar

There has been always an interaction between geomorphic landforms and vegetation type and density. Alluvial fans are among landforms having considerable effect on vegetation. Sabzevar region in Khorasan Razavi Province, due to its various and typical alluvial fans, is suitable location for studying the geomorphology/vegetation relations. The aim of this study is qualitative and quantitative assessment of vegetation type and density in abandoned, old and young fans in south of Foshtanq village. Results were obtained from identification of three alluvial fan borders based on topographic maps, satellite images and field works and from determining vegetation type and canopy, soil analysis and finally the relations between mentioned parameters were identified. Results show that gullies on abandoned fan, due to their coarser texture, are adequate for shrubs. Vegetation of abandoned fan’s gullies has highest amount of canopy (10.676%) because of sufficient moisture drained from interfluves while the vegetation on active channels of old and young fans has lowest canopy (0.58 % for young fan and 0.887% for old fan). In abandoned fan, vegetation canopy is higher in gullies than interfluves, while in old fan, it is higher in interfluves than gully beds. Dominant vegetation species in old and young fans include Artemisia seiberi and Astragalus squarasus in interfluves and Pteropyrum aucheri in channels. In abandoned fan, dominant species are Artemisia seiberi and Scariola orientalis. Overall, results show that geomorphological processes such as incision and deposition influence the soil texture and fertility and hence vegetation type and density.