The effects of soil salt crusts on soil evaporation and chemical changes in different ages of Taklimakan Desert Shelterbelts

Understanding soil evaporation in reforestation processes in an area of extreme drought is important. We examined the effects of drip-irrigated, high-salinity groundwater on the formation of soil salt crusts and subsequent soil evaporation in the Taklimakan Desert Highway Shelterbelt. Soil evaporation was measured using micro-lysimeters (MLS, 20 cm in length × 10 cm in diameter), and chemical characteristics, including SOM, total salts, ion composition and pH, were analyzed. The results showed that the inhibition efficiency of salt crusts on soil evaporation decreased from the surface to the lower soil layers. Following irrigation, the inhibition efficiency was 33.0% in the shelterbelt, which was much higher than the 13.8% observed for the bare soil. Total salt content and ion contents (Cl-, Na+, and SO4 2-) were much higher for the soil salt crusts than for shifting sandy soils, while the contents of other ions (Mg2+, K+, Ca2+, HCO3 -, and CO3 2-) were very similar. The total salt content and ion composition of the salt crusts increased during the first 2 years of shelterbelt age, and decreased from 2 to 5 years. With the increasing age of the shelterbelts, the SOM of the salt crusts increased, whereas the total salts and pH decreased. We concluded that the formation of soil salt crusts results in reduced soil evaporation and the soil chemical condition functioned better for growth of the Taklimakan Desert Highway Shelterbelt.