Abstract:

【Objective】 The objective of this study was to understand the response of soil Ca and Mg geochemical recycle in rice paddy ecosystem to elevated atmospheric CO2. 【Method】 Field experiment was carried out at Experiment Station of FACE (free-air carbon dioxide enrichment) in China. There were two treatments, including ambient (the CO2 concentration was approximately 370 μmol?mol-1) and FACE (the target CO2 concentration was 200 μmol?mol-1 higher than that of ambient). Soil solution samples were collected in situ at different stages during the 2004, 2005 and 2007 rice growing seasons. Concentrations of Ca and Mg in soil solution were determined. 【Result】 The concentrations of Ca in soil solution at 5 cm depth in FACE treatment were 25%, 6% and -28% higher than those in ambient treatment during the 2004, 2005 and 2007 rice growing seasons, respectively. The ratios of 15cm/5cm of Ca and Mg in soil solution from FACE treatment were -29%, 14% and 80% and -26%, 4% and 59% higher than those from ambient treatment during the 2004, 2005 and 2007 rice growing seasons, respectively. The concentrations of Ca and Mg in soil solution at 0-15 cm depth in FACE treatment were less than ambient treatment by 6.8% and 4.6% in the year of 2007, respectively. 【Conclusion】 Elevated atmospheric CO2 influenced the distributions of Ca and Mg in soil solution at different depths in arable layer and increased the ratios of 15 cm/5 cm of Ca and Mg in soil solution. This indicates that elevated atmospheric CO2 has a potential impact of soil Ca, Mg in the biogeochemical cycles, and may affect rice yield and quality.

Key words: elevated CO2, soil solution, Ca, Mg, paddy ecosystem