土壤腐殖质组成对大气二氧化碳浓度升高的响应

Responses of Fractions of Soil Humus to Free-Air CO_2 Enrichment

为了探求大气CO2浓度升高对土壤腐殖质及其组成的影响，为大气CO2浓度升高条件下土壤生物化学过程的变化提供依据，通过稻-麦轮作FACE（Free-air CO2 enrichment）平台研究了正常施氮水平下水稻土壤有机碳及其各组分对大气CO2浓度升高的响应。研究结果表明：不同土层的腐殖质组分含量有所差异，表层（0～15cm）土壤腐殖化程度较高，表层的土壤有机碳（SOC）、水溶性碳（WSOC）、胡敏酸（HA）、富里酸（FA）、胡敏素（HM）数量均高于下层（15～30cm）。大气CO2浓度升高，增加了表层和下层的SOC，促进了土壤有机质的积累；使表层WSOC有增加趋势，但对下层没有显著影响；降低了土壤中可提取腐殖物质中HA的比例（PQ），土壤的腐殖化度下降，有利于HA的分解与转化和FA的积累；对土壤HM没有显著影响。

It studied the effects of Free-air CO2 enrichment （FACE） on soil humus and its fractions, which can provided scientific basis for the transformation of soil biochemistry. The responses of soil organic carbon （SOC） and its fractions of paddy field to FACE were studied under natural nitrogen fertilization by FACE experimental system of paddy-wheat rotation. The results showed that the fractions contents of soil humus were different in different soil layer. The amounts of SOC, water-soluble organic carbon （WSOC）, humic acid （HA） and humin （HM） in the surface layer of soil （0-15 cm） were more than that in the substrate （15-30 cm）. Under the condition of elevated CO2 concentration, the amount of SOC increased in the surface and substrate, soil organic matter was accumulated. The amount of WSOC increased in the surface layer, but it was not affected in the substrate. HA proportion in the extracted humus （PQ） and degree of humification of soil was dropped. Elevated CO2 concentration was beneficial to the decomposition and transformation of HA and the accumulation of FA; HM was not affected significantly.