EFFECT ON SOIL PROPERTIES OF CONVERSION OF YELLOW RIVER DELTA ECOSYSTEMS.

Using remote sensing and geographic information system technologies, we analyzed changes in ecosystem boundary conditions in the Yellow River Delta. We investigated variations in soil water, bulk density, total nitrogen, total phosphorus, and organic matter, as well as concentrations of soluble Ca²⁺, Mg²⁺, and Na⁺, under different ecosystem conversions. Results indicated that from 1992 to 2006, boundary characteristics became more complicated and ecosystem conversion was mainly from farmland to a mixed ecosystem supporting Tamarix chinensis-Phragmites communis. These ecosystem conversions may be attributed to a combination of urban expansion, oil exploration and extraction, water interception, and soil salinization. Ecosystem conversion also affected soil properties. Organic matter differed among the ecosystems, as did the concentrations of the soil base cations. Ca²⁺ concentration was higher than concentrations of other cations, and significant differences existed in Ca²⁺ and Mg²⁺ concentrations among ecosystems. While the concentration of K⁺ and Mg²⁺ showed similar concentrations, mostly increasing, among different ecosystem conversions, Na⁺ concentrations decreased. In summary, the concentrations of soluble minerals were significantly influenced by ecosystem conversions. [ABSTRACT FROM AUTHOR]