Investigation on changes in soil organic matter and nutrient elements under various grazing intensities (Case study: Chaharbagh mountain rangelands of Golestan province)

Soil, plant and livestock are the main and active components of rangeland ecosystems and have close relationship with each other so that changes in the characteristics and composition of each component affect other components directly and indirectly. This research was conducted in order to survey the effect of various grazing intensities on soil organic matter and nutrient elements in mountain rangelands of Chaharbagh in Golestan province. Thus, five rangeland sites including exclusion site (reference), key site, critical sites such as watering site, vicinity of village and resting site were selected and soil sampling was conducted in two depths of 0-20 and 20-40 cm, with regard to the depth of rooting, using random-systematic method in the end of grazing season. Then, soil properties such as organic matter (OM), total nitrogen percent (TN%), absorbable phosphorous (P), potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg) of each soil sample were determined in laboratory. Data analysis and mean comparisons were performed by two-way analysis of variance and Duncan test, respectively. Results showed that site, depth and interaction effects were significant in various sites in all parameters with the exception of Na and Mg, and various grazing intensities had significant difference in study parameters. In general, with increasing grazing intensity, the amount of OM, N, P and K decreased with the exception of resting site. Meanwhile, the mean of nutrient elements and organic matter in reference and key sites were similar and highest, indicating the necessity of considering the balance between livestock and rangeland, suitable distribution of livestock and consequently preventing intensive grazing in order to maintaining the sustainability of rangeland ecosystems.