Land exploitation resulting in soil salinization in a desert–oasis ecotone

Understanding the process of agricultural land expansion and its impact on soil properties is crucial for land management and environmental health. A desert–oasis ecotone is typically located between an oasis at the lower reach of inland rivers and neighboring desert in arid regions, and acts as an interactive zone between irrigated farmland and the natural desert ecosystem. The arid region of northwest China has experienced dramatic land exploitation since the 1960s and soil salinization has been a serious environmental problem ever since. The objective of this study was to determine the relationship between land exploitation and soil salt accumulation in the topsoil. A typical desert–oasis ecotone, the Fubei region at the lower reach of the Sangong River catchment in arid northwest China, was used as a case study. The results revealed the following: (1) 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. (2) 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>20g/kg increased by 16.4%, while the area with soil salt content of 5–10g/kg decreased by 42% during 1982–2009. In addition, the amount of overall soil salt accumulation was about 21.6×1010g 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). (3) The dramatic salt accumulation was a result of agricultural land exploitation that requires irrigation, and this directly caused a rising groundwater table, and then higher evaporation led to soil salinization. Collectively, the results indicate 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.