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Original Article

The Response of Topsoil Properties and Nitrogen Transformation to Land Cover in a Semi-arid Rangeland (Case Study: Kojur Rangeland in Mazandaran Province, Iran)



The role of different plant covers (i.e. Artemisia aucheri Boiss, Cousinia commutate Bunge and Agropyron longiaristatum Boiss) in topsoil properties and Nitrogen transformation is less known under semi-arid mountains. The main objective of this research was to study the effect of land covers on topsoil properties and nitrogen transformation. The study was carried out for investigating the soil properties of Grazing Exclusion (GE), Grazed Rangeland (GR) and Rainfed Agriculture (RA) in Kojur, Mazandaran province, Iran. Thirty-six 1m2 plots were set at three treatments to sample the dominant plant species. Soil samples were then taken from the central part of each plot sample in an area of 20×20 cm and depth of 20 cm. Our findings demonstrated that the carbon (C) content of plant materials did not differ for studied land covers whereas GR and RA had higher N content (1.48 and 1.41%, respectively) and lower C/N ratio (13.33 and 14.45%, respectively). In the GE, N concentration of soil (with 0.34%) was 1.5 times more than that in GR and RA (0.20 and 0.21%, respectively). Soil nitrification and N mineralization rates were significantly higher in the GE (0.33 and 0.28 mg kg−1d−1 respectively) as compared to the RA (0.15 and 0.08 mg kg−1d−1 respectively) and GR (0.01 and 0.04 mg kg−1d−1 respectively). There were no significant differences among land covers for bulk density, available K, microbial respiration, and ammonification rates. According to the results, grazing exclusion with presence of grass species increases the organic C contents, total N, and eventually, N mineralization which totally leads to improved soil quality in these regions.