大气CO2浓度升高对稻田土壤Ca、Mg迁移的中长期效应

为了进一步认识稻田土壤中Ca、Mg元素生物地球化学循环对大气CO2浓度升高的响应，本实验利用中国稻麦轮作FACE(free air carbon-dioxide enrichment)试验平台，通过观测稻季不同生育期不同深度(30、60和90 cm)土壤溶液中的Ca2+、Mg2+ 浓度，研究大气CO2浓度升高对土壤Ca、Mg淋移的中长时期(第9年)影响。研究结果表明，随着土壤深度的增加，土壤溶液中的Ca2+浓度呈降低趋势，Mg2+浓度呈增加趋势；随着生育期的推进，呈现先增加后减小的趋势，并在抽穗期达到最大值。大气CO2浓度升高略微降低30、60 cm处土壤溶液的Ca2+ 浓度，增加90 cm处Ca2+ 浓度(6.7%)。稻田不同深度土壤溶液中Mg2+ 浓度对大气CO2浓度升高的响应有所不同，且在60 cm处有较强的正响应(12.1%)。研究明确高浓度CO2有加剧Ca2+、Mg2+ 向下淋溶损失的趋势，耕层土壤有机物料输入增多、 浓度增加、pH下降等是主要原因。大气CO2浓度升高对农田生态系统土壤Ca、Mg元素循环的长期影响值得进一步关注。

Medium-long Term Effects of Elevated Atmospheric CO2 on Transposition of Ca and Mg in a Rice Paddy Field

To further investigate the response of biogeochemical cycle of Ca and Mg to atmospheric CO2 enrichment, a study associated with the medium-long term effects of elevated CO2 on transposition of Ca and Mg at three soil depths (30, 60, and 90 cm) in different developmental stages was carried out on China rice-wheat rotation FACE (Free Air Carbon-dioxide Enrichment) experimental platform in the rice growing season. The results showed that with the increment in the soil depth, the Ca2+ concentration in soil solution showed a trend of decrease, and the Mg2+ concentration was increasing; whereas they increased at first and decreased then, and peaked at heading stage. Atmospheric CO2 enrichment slightly decreased the Ca2+ concentration in the soil solution at 30 and 60 cm, but enhanced it at 90 cm (6.7%). It was detected that the responses of Mg2+ concentration in the soil solution to elevated CO2 differed with the soil depth, and a stronger positive response was found at 60 cm (12.1%). This study indicated that elevated CO2 tends to intensify the leaching loss of Ca2+ and Mg2+, the increase in organic materials input andconcentration, and decrease in pH in the plow layer are the main causes. The long term effects of elevated CO2 on Ca and Mg cycle in the soil under agricultural ecosystems deserve a further attention to pay.