Abstract: Based on the investigation of the characteristics of degenerated Haloxylon ammodendron populations, soil physical and chemical properties, and groundwater level in west Gurbantonggut Desert, a cause analysis was made on the degeneration of H. ammodendron in the area. In the study area, most of the soils were heavily salinized, and the trees and seedlings were sparse, with an average coverage being only 11.58%. The age structure diagram indicated that the H. ammodendron populations were in declining. There was a significant negative correlation between the individual viability of H. ammodendron and the soil conductivity in 0-40 cm and 40-80 cm layers (r=-0.79, P=0.000; r=-0.32, P=0.009), and a significant positive correlation between the individual viability and the soil moisture content in 80-120 cm layer (r＝0.54, P=0.000). The survival index and coverage of the H. ammodendron populations were significantly correlated with groundwater level (r²=0.40, P=0.007; r²=0.46, P=0.004). It was concluded that the declining groundwater level, inadequate soil moisture, and high soil salt content were the main factors causing H. ammodendron degeneration.

Key words: Heavy metal, Pollution protection, Greening tree species