Dynamics Of Soil Water, Temperature, and Salt and Their Coupled Effectsin Haloxylon Ammodendron Forests of Different Ages in an Arid Desert Oasis Ecotone

Study region: A typical desert oasis ecotone of the Hexi Corridor, Northwest China.Study focus: Based on four years of in situ observation data of soil water, temperature, and electrical conductivity obtained at three Haloxylon ammodendron (H. ammodendron) forests (20, 30 and 50 years) in a typical desert oasis ecotone (DOE) of the Hexi Corridor, this study first presented the change mechanisms and coupling effects of water, heat, and salt in frozen desert soils along a long-term shrub plantation in a typical desert oasis ecotone.New hydrological insights for the region: This study found that changes in soil water, heat, and salt and their coupled effects were totally different between shallow (0–80 cm) and deep depths (160–200 cm). At 0–80 cm, soil water gradually decreased in the 50-year-old H. ammodendron plantation, but soil salt first increased at 30 years and then decreased at 50 years. When the freezing process occurred at the 0–80 cm depths, the soil water and saltdecreased nonlinearly with the absolute value of soil temperature, following a power function and logarithmic function, respectively. For the thaw process at the 0–80 cm depths, soil water and salt increased with increasing temperature, and there was a significant linear relationship between soil water and salt (P<0.01). At 160-200 cm, soil water and salt significantly increased after 30–50 years during the growing season.