Characteristics of landscape geochemistry in Karamay artificial carbon-sink forests

Karamay artificial carbon-sink forest is located in the southern margin of Gurbantunggut Desert, where soil salinization is a severe ecological problem. With adequate knowledge on the patterns of soil soluble salts/ions distribution, mechanisms of change, chemical constituents of groundwater and varied characteristics of landscape patterns, saline soils can be rationally utilized and ecological agro-forestry efficiently developed. This paper aimed to lay the theoretical basis for ameliorating soil salinity and controlling desertification via analyzing the characteristics of Karamay landscape geochemistry. Using monitoring field data for soil soluble salt, groundwater salinity and vegetation cover in Karamay artificial carbon-sink forest, the characteristics of landscape geochemistry were analyzed via descriptive statistics and correlation analysis. The results showed great variation in contents of Cl^-, SO₄^2-, Ca²⁺ in 0~80 cm soil, while less variation in salinity and salt ions contents in 80~100 cm soil layer was found. Soil salinity increased with increasing soil evaporation resulting in severe salt accumulation in surface soils of Karamay carbon-sink forest. Sulfate was the dominant salt in study area, which consisted mainly of soluble SO₄^2- and Na⁺ and K⁺ salts. With the exception of HCO₃^-, variations in groundwater salinity and the related compounds exhibited strong variation. Cl^-, SO₄^2-, Na⁺ and K⁺ were the main elements of groundwater mineralization, and significant linear correlations were noted among salinity and these ions. The groundwater chemical type was Cl·SO₄-Na. Forest protection ameliorated soil salinity. Although the dynamics of soil salinity varied from forest to forest, salinity (more for SO₄^2- salts) dropped after planting forests. Furthermore, soluble total salts significantly dropped with increasing age of the Russia poplar forest.