Effect of Land Use on the Carbon Stock and Soil Quality Attributes in Loess Derived Soils in Agh-Su Watershed, Golestan Province, Iran

Monitoring the effect of land use on soil quality attributes within an ecosystem can provide a useful way to control land degradation and achievement of sustainable management. In order to study the effects of different land uses on carbon stock and soil quality attributes, a loess hillslope was selected in eastern Golestan Province, Agh-Su area. Six pedons in four land uses including pasture; Oak natural forest; Cypress plantation forest and a cultivated land, were studied. Important physical, chemical and biological soil quality attributes such as bulk density (Bd), mean weight diameter (MWD), cation exchange capacity (CEC), available P, Biomass carbon (BioC) and Soil Microbial respiration (SMR) were studied. The results revealed that cultivation has led to the deterioration of soil quality attributes. Organic matter, CEC and MWD were significantly lower in the cultivated land. MWD varied between the highest 2.36 mm in the Oak natural forest and the lowest 0.54 mm in cultivated land. Soil organic carbon stock in the forest and pasture area was considerably higher than that of the cultivated land. Soils classified as Calcic Argixerolls and Typic Calcixerepts were formed under the Oak natural forest and the cultivated land respectively. Soils of the pasture and the Cypress forest were classified as Typic Calcixerolls. Micro-morphological studies revealed that size and frequency of microcrystalline calcite nodules and coatings increase from cultivated land to pasture. Cytomorphic and acicular calcite were observed mainly in the Oak natural forest and a denser vegetative growth, but rarely in cultivated areas.