The Comparison of Soil Loss and Sediment Yield of Some Geology Formations in Plant Vegetation Gradients (Case study: Summer Rangelands of Balade in Mazandaran Province)

Vegetation cover as the main factor affecting the water erosion plays an important role in preventing soil loss. To this end, for better understanding the impact of vegetation cover on soil erosion and sediment yield over the major existing geological formations in the summer rangelands of Balade in the Mazandaran province, rainfall simulation studies have been carried out using a portable rainfall simulator. Among many geological formations across the study area, the three major lithological units of mica sandstone, clay and shale sandstone with coal seams of “SHEMSHAK”, structures of tuff shale and dark gray to green shale with volcanic rocks of “KARAJ” and limestone of “LAR” have been selected as lowly, moderately and highly resisting formations to degradation. For each combination of geological formation and vegetation cover (low, moderate, and high density) three sampling plots of 1x1m have been selected and rainfall simulation has been conducted over them. For each plot, the surface characteristics including the vegetation cover, runoff and sediment yield and soil texture were measured. The measured data were statistically analyzed. Results showed that “SHEMSHAK”, “KARAJ” and “LAR” formations were respectively ranked from highest to lowest with respect to the volume and weight of sediment yield. Also, there was a strong inverse relationship between vegetation cover percentage and volume of runoff and sediment for all investigated geological formations specially in poor vegetation situation that indicate interaction effects between vegetation cover and type of geological formations.