Effect of life form and vegetation cover on runoff and sediment yield in rangelands of Savadkooh region, Mazandaran

Soil erosion is the most serious threat for environment، agriculture and food production in the world. It has deleterious effects on natural and human-managed ecosystems. These impacts are related to land use and management. Soil erosion starts as vegetation degraded. This study aimed to assess the effect of plant life form and cover on soil runoff and sedimentation. It was carried out in three major life forms (grasses، forbs، and shrubs) in mountainous rangelands in Savadkooh، Mazandaran province in Iran. For grasses 10 plots of 100 m2 and for other two life forms 7 plots of 100 m2 were established and then in each 100 m2 plot a number of 6 microplots (30 x 30 cm) were selected randomly. Different amount of vegetation cover was made in each microplot by clipping. These were 100%، 50% and bare ground (0%) each with two replicates. Then we applied rainfall simulator in each microplot to measure runoff volume، sediment concentration، sediment yield، runoff initiation threshold and runoff coefficient. Results showed that both life form and vegetation cover significantly influenced the amount of runoff and sedimentation. Greatest runoff was found for forbs while grasses had lowest amount of runoff. Also bare ground and 100% cover showed the greatest and least amount of runoff، respectively. The concentration of sediment for shrubs was significantly greater than grasses and in 100% cover it was significantly lower than 50% and bare ground.