Soil Bio-physicochemical Properties Changes in Response to Grazing Intensity and Seasonal Variations in an Arid Rangeland Ecosystem of Iran

Aims: This study investigates the response of some soil bio-physicochemical properties under different grazing intensities management in a 17-year-old arid rangeland ecosystem of Iran. Material Methods: The grazing intensity gradient was as follows: (1) without herbivore grazing over a whole year (NG), (2) grazing by sheep and goats done communally from November to May (RG), and (3) continuous and heavy grazing over a whole year (HG). The soil samples were collected from the upper 20 cm in November and May.  Findings: The significantly higher bulk density values (P 0.05) were measured with increasing grazing intensities, i.e., 1.65, 1.82, and 1.96 g.cm-3 in NG, RG, and HG, respectively. The management system affected significantly (P 0.05) organic carbon (OC), total nitrogen (TN), available phosphorus (P), exchangeable potassium (K), as well as enzyme activity of acid- and alkaline phosphatase (ACP, ALP) and urease. Similarly, the time of sampling affected significantly (P 0.05) OC, P, C, ACP, ALP, and urease activity in the soil. The soil OC ranged from 0.46 to 2.78 %, K ranged from 51.81 to 92.06 ppm, TN and P showed significantly (P 0.05) higher HG and RG values than NG. The soil pH ranged from 7.89 to 8.32, and EC (electric conductivity) ranged from 0.47 to 0.93 dS.m-1, which was significantly affected neither by the grazing management system nor by sampling time. The TN showed a high positive correlation with ALP (r = 0.89), urease (r = 0.72), and dehydrogenase (r = 0.76). The OC, P, ACP, and ALP responded more sensitively to grazing management systems. Conclusion: The presence of animals in our study site positively affected soil fertility. However, similar studies are required to complete our knowledge under different climatic conditions, vegetation-grazer types, and grazing duration.