Land Exploitation Resulting in Soil Salinization in the Lower Reaches of the Sangong River Catchment, Xinjiang

Soil salinization is a long-standing environmental problem in the world, especially in arid or semiarid regions. It is a major environmental threat affecting soil properties and reducing soil productivity. Thus, more effort is needed to improve productivity as more land becomes salinized. However, in previous studies on land-use changes, limited attention had been paid to soil salinization in arid regions.

Desert-oasis ecotones are typically located between an oasis at the lower reach of inland rivers and the neighboring desert in an arid area, and act as an interactive zone between irrigated farmland and the natural desert ecosystem. Maintaining stability in a desert–oasis ecotone could effectively prevent land degradation/salinization in the oasis.

Understanding the process of agricultural land expansion by human activity and its influence on soil properties is crucial for land management and environmental health. Therefore, quantifying the spatial and temporal changes in land use and soil salinization is important to identify the locations and extent of soil salinization during the course of agricultural land expansion.

To determine the relationship between land exploitation and soil salt accumulation in the topsoil, Dr. WANG Yugang and Prof. LI Yan from XIEG selected a typical desert–oasis ecotone, the Fubei region at the lower reach of the Sangong River catchment in arid northwest China as the study area.

The results revealed that overexploitation of land resources has been astonishing since 1960, with >40% of the area becoming irrigated farmland. There was frequent transition of land-use types from one to another, with about 38% of the area experiencing transitional change during 1982–2009. Comparing soil salt content with land use during 1982–2009 showed an expanding area of soil salinity and an increased degree of salinity in all land-use types. The area with soil salt content>20 g/kg increased by 16.4%, while the area with soil salt content of 5–10 g/kg decreased by 42% during 1982–2009.

In addition, the amount of overall soil salt accumulation was about 21.6×10¹⁰ g in the study area during 1982–2009, and soil salt accumulation per unit area increased by 60%, with salt accumulation in farmland, grassland and saline-alkali land higher than for other land-use types (p<0.05). The dramatic salt accumulation was the result of agricultural land exploitation. In the study area, agricultural land exploitation directly caused a rising groundwater table, and then higher evaporation led to soil salinization.

This study indicated that overexploitation of land resources had large and prolonged effects on soil salinization, which is a lesson to be learned for integrated land management in similar ecotones in arid zones. The result was published in Catenaon 2013, 100: 50-56.