Assessing the impacts of land use and land cover changes on soil functions using landscape function analysis and soil quality indicators in semi-arid natural ecosystems

Assessing soil quality indicators is essential for ecosystem function evaluation. This study aimed to compare soil quality indicators of semi-arid forests and rangelands with different condition classes using direct soil quality indicators and landscape function analysis (LFA). Vegetation and soil properties were studied in three forest sites with different densities and 16 rangeland sites. A total of 72 soil samples were collected from various land use/cover types and their physical and chemical properties were measured. Eleven soil quality indicators were assessed from each patch and inter-patch zone along the established transects in each land use/cover type to obtain three functional indices including soil stability, infiltration, and nutrient cycling. The accuracy of the stability and infiltration indices of the LFA was verified by their correlations with some soil quality indicators. The results revealed a similar trend in soil quality indicators among the land use/cover types indicating that soil organic carbon (SOC), particulate soil organic matters (POM), mean weight diameter (MWD), soil stability index (SSI), and macronutrients had more appropriate conditions in rangelands with good conditions and dense forest sites compared to other land uses/covers. The soils in rangelands with poor conditions and sparse forests required substantial input of organic carbon to achieve an appropriate level of soil quality. The results highlighted the importance of SOC, POM, and soil texture for the prediction of aggregate stability in the region. The regression model showed a significant relationship between MWD and SSI. Moreover, nitrogen and SOC had significant relations with nutrient cycling and the relation between water dispersible clay and infiltration index was also significant (p < 0.01). The methods used in this study underscored the importance of conserving natural ecosystems. These methods can be implemented for assessing other semi-arid ecosystems. Holistic land management is required to conserve natural and productive ecosystems and to prevent soil degradation.