稻田水体可溶性有机碳与可溶性氮对大气CO2浓度增高的响应

为了增强对全球变化背景下湿地生态系统碳氮循环的整体认识,采用稻田FACE(Free Air CO2Enrichment)试验(位于江苏省江都市,始于2004年)方法,研究了2006年位于江都市的稻田水体中总有机碳、总氮、可溶性有机碳、可溶性氮的动态变化.结果表明:大气CO2浓度升高显著提高了稻田水体中以上各指标含量(p<0.01),其中各有机碳的增幅均大于相应的氮.与对照相比,FACE田块水体中总有机碳、总氮、可溶性有机碳和可溶性氮分别平均提高了31.2%、25.9%、28.3%和25.6%.不同生育时期各指标含量存在显著差异(p<0.01).上述结果还表明,大气CO2浓度增高不仅会通过富营养化稻田水体来影响水稻安全生产,而且还会提高其中可溶性碳氮含量,进而可能通过田间排水尤其是水稻生长前期暴雨导致的洪涝来增加稻田碳氮向周边水域的输送,从而影响到稻田生态系统的碳氮循环和土壤生产力.

Responses of dissolved organic C and N in paddy field water to elevated atmospheric CO2

In order to enhance our understanding of carbon and nitrogen cycle in wetland ecosystem, total organic carbon (TOC), total nitrogen (TN), dissolved organic carbon (DOC) and dissolved nitrogen (DN) in the paddy field water were monitored dynamically by Free Air CO2 Enrichment (FACE) of paddy field(started in 2004, located in Jiangdu County, Jiangsu province). The results showed that elevated atmospheric CO2 significantly increased TOC, TN, DOC and DN by 31.2%, 25.9%, 28.3% and 25.6% on average, respectively, than those in ambient plots (P<0.01). There were significantly differences in TOC, TN, DOC and DN between different rice growing stages (P<0.01). The results also indicate that elevated atmospheric CO2 could threat rice security production through eutrophicating paddy field water and increase aquatic DOC and DN. Therefore elevated atmospheric CO2 may influence the rice ecosystem C and N cycle and soil productivity through field drainage and rainstorms at the early stage of rice.