Abstract
This study aims to examine the changes in soil chemical properties (soil organic matter, SOM; available nitrogen, AN; available phosphorus, AP; available potassium, AK; total nitrogen, TN; total phosphorus, TP and pH) in three depths (i.e. 0-5, 5-10, 10-20 cm) from different land use types of the Green Beach Desert-oasis Ecotone, Inner Mangolia, China. Using soil chemical properties data, comprehensive soil quality index (SQI) was calculated based on principal component analysis (PCA) of variables across different soil depths for different land use types. Results showed that soil properties differed significantly according to land use type. The eight land use types all showed decreases in TN and TP meaning values for these variables fell below those measured from the control plot (bare ground or 'CK'). Farmland and protective forest soils showed higher AK, AN, AP and SOM contents with protective forest soil the higher of the two. This contributed to accumulation of soil nutrients. Soil quality index results showed that the soil quality index of abandoned farmland in 5-10 cm and 10-20 cm soil layer is the highest among the eight types of land, therefore, the 5-10 cm and 10-20 cm soil layers of abandoned farmland could help to optimize soil nutrients. The 0-5 cm layer of the protective forest soil also showed obvious nutrient accumulation. These results provide basic reference data and trends for soil quality assessment in arid, ecologically fragile areas.