EFFECT ON SOIL PROPERTIES OF CONVERSION OF YELLOW RIVER DELTA ECOSYSTEMS Min Yang 1 , Shiliang Liu 1 , Zhifeng Yang 1 , Tao Sun 1 , Stephen Daniel DeGloria 2 , and Kathleen Holt 3 1 School of Environment State Key Laboratory of Water Environment Simulation Beijing Normal University Beijing, China 100875 E-mail: shiliangliu@bnu.edu.cn 2 Department of Crop and Soil Sciences Cornell University Ithaca, New York, USA 14853 3 Department of Family Medicine University of Rochester New York, USA 14620 Abstract: 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 Ca 2+ ,K + , Mg 2+ 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. Ca 2+ concentration was higher than concentrations of other cations, and significant differences existed in Ca 2+ and Mg 2+ concentrations among ecosystems. While the concentration of K + and Mg 2+ 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. Key Words: boundary characteristics, ecosystem conversion, soil chemistry INTRODUCTION As a fundamental resource and basic component of any ecosystem, soil plays a major role in biogeochemical cycles (Fu et al. 2000, Zhao et al. 2007). The conversion of an ecosystem (for example, from river delta to farmland) and implementation of different management measures may cause signifi- cant variation in soil properties (Braimoh and Vlek 2004, Jiang et al. 2006). These properties may include soil water (Fu et al. 1999) and nutrients (Falkengren-Grerup et al. 2006) such as organic matter, total nitrogen, total phosphorus, as well as changes in ecological processes (Sernwal et al. 2004). At both regional and global scales, ecosystem conversion is an important factor for biogeochem- ical processes, and wetland change specifically has a great effect on regional biogeochemical cycles (Liu et al. 2003). Analyses of long-term ecosystem conver- sions indicate relative stability in some wetlands but succession in others (Steven and Toner 2004). Investigations of wetland change have often focused on the conversion of wetland types to non-wetland types, while studies of conversions among different wetland types have been more limited (Bai et al. 2003). Available studies have shown that land use changes in river basins or areas around lakes (Merot et al. 2003) have impacts on soil properties (Szilassi et al. 2006, Chen et al. 2007). However, effects of ecosystem conversion on soil properties in estuaries or deltas remain virtually unknown (Qin et al. 2007). Although significant changes in land use (Bunkei et al. 2006) and variability of soil properties (Yao et al. 2006) have been comprehensively assessed, the WETLANDS, Vol. 29, No. 3, September 2009, pp. 1014–1022 ’ 2009, The Society of Wetland Scientists 1014