Impact of slope and rock layers of conglomerate and sandstone lithology on vegetation cover in arid lands (Case study: Lamerd, Fars province)

Lithology of large part of Lamerd rangelands in south of Fars province is Bakhtiari geology formation. Sandstone and conglomerate rocky slopes in this geology formation were analyzed in this study area. Then, several factors affecting on plant canopy were evaluated in both field and laboratory studies. In regard to the changes resulting from water erosion and slope, areas with the slopes of less than 100% (perpendicular to the layers along rocky) and slopes of more than 100% (on rock layers) were selected for taking samples. In each site, 35 transects with a length 5 m were randomly laid out throughout the study area in north aspect and along those transects, percentage of vegetation cover and numbers of large crack wide, medium crack wide, small crack wide, large crack depth, medium crack depth, small crack depth, large crack length, medium crack length, small crack length were measured. In addition, laboratory tests were conducted to measure soil characteristics and moisture content of the soil inside the cracks. Analysis of soil properties showed that the moisture content was significantly differed (p<0.05) among the three depths of 0-10, 10-30 and 30-50 cm in both sandstone and conglomerate rocky. But, the differences between other soil properties were insignificant statistically. Results indicate that there are significantly differences between crack properties in vegetation cover in the conglomerate and sandstone rocks and between two slope classes in each rock. Moreover, vegetation cover has positively significant relationships with increase of crevice wide and depth in each lithologic unit. It was concluded that the differences of crevice properties could be prominent role in vegetation cover changes in the crevice characteristics could be related to rocky type and stratigraphy in different slopes.