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 preventingsoil loss. to this end, for better understanding the impact of vegetation cover on soil erosion andsediment yield over the major existing geological formations in the summer rangelands of balade inthe mazandaran province, rainfall simulation studies have been carried out using a portable rainfallsimulator. among many geological formations across the study area, the three major lithological unitsof mica sandstone, clay and shale sandstone with coal seams of “shemshak”, structures of tuffshale and dark gray to green shale with volcanic rocks of “karaj” and limestone of “lar” havebeen selected as lowly, moderately and highly resisting formations to degradation. for eachcombination of geological formation and vegetation cover (low, moderate, and high density) threesampling plots of 1x1m have been selected and rainfall simulation has been conducted over them. foreach plot, the surface characteristics including the vegetation cover, runoff and sediment yield and soiltexture were measured. the measured data were statistically analyzed. results showed that“shemshak”, “karaj” and “lar” formations were respectively ranked from highest to lowestwith respect to the volume and weight of sediment yield. also, there was a strong inverse relationshipbetween vegetation cover percentage and volume of runoff and sediment for all investigatedgeological formations specially in poor vegetation situation that indicate interaction effects betweenvegetation cover and type of geological formations.