Assessment of the Effects of Overgrazing on the Soil Physical Characteristic and Vegetation Cover Changes in Rangelands of Hosainabad in Kurdistan Province, Iran

Soil physical properties have an important role on vegetation growth through affecting the development of root system. The aim of this study was to investigate the trampling effect of livestock grazing on soil physical properties and vegetation cover changes. The experiment was conducted on three range condition sites (Reference, Key and Critical area) with ten frequencies in Hosseinabade Kudistan in 2009. Soil physical characteristics consist of humidity, bulk density, porosity and aggregate stability index. In this study remarked soil cover changes in three mentioned regions. The results showed that soil moisture reduced from reference to critical area. Soil bulk density was the lowest in reference area and the highest in critical area. Reference site had the highest soil porosity while the soil porosity reduced in critical area. However, as the density of grazing increased, soil bulk density increased and soil moisture, soil porosity, aggregate stability index and vegetation cover percent decreased. Bare soil percentage was the highest in critical region. According to the results of this research, the grazing seems caused to major changes in the physical properties of the topsoil. Since the region has high ecological potential, if the intensity of grazing would be in a moderate level, the region soil will be able to compensate the negative aspects of livestock trampling.