可溶性有机碳的含量动态及其与土壤有机碳矿化的关系

采用我国东部地区的黑土、潮土、黄泥土和红壤水稻土,通过室内分析和培育试验,研究了不同水分条件下可溶性有机碳含量及土壤有机碳矿化量的动态变化,分析了淹水导致可溶性有机碳含量的变化程度及其对土壤有机碳矿化量的可能影响.结果表明,可溶性有机碳含量与水土比呈直线相关关系,累计提取量随浸提时间增加,单次提取量随提取次数降低.在8周的培养期内,淹水处理的可溶性有机碳含量均显著高于好气处理,黄泥土一号高46%～117%(p＜0.05),黄泥土二号高112%～285%(p＜0.001),潴育黄泥田高21%～73%(p＜0.05).在培养的前3周(黄泥土一号)或前4周(黄泥土二号),不同水分处理的日均土壤有机碳矿化量有极显著差异(p＜0.01),其后,差异不显著;但在整个培养过程中,淹水处理的累计土壤有机碳矿化量均极显著高于好气处理(p＜0.01).培养过程中,土壤有机碳的矿化速率动态与可溶性有机碳含量的变化趋势相一致,特别是黄泥土二号,可溶性有机碳含量与土壤有机碳日均矿化量达到极显著的相关关系(好气相关系数0.942,淹水相关系数0.975).结果还表明,两种黄泥土有机碳矿化量(包括日均矿化量和累计矿化量)的差异并不与全土有机碳含量相关,而主要是其可溶性有机碳含量明显不同所致.因此,对于原土可溶性有机碳含量较高的土壤,淹水显著提高可溶性有机碳量是导致其土壤有机碳矿化量高于好气处理的主要原因.

DYNAMICS OF SOLUBLE ORGANIC CARBON AND ITS RELATION TO MINERALIZATION OF SOIL ORGANIC CARBON

Mineralization of soil organic carbon is an important biochemical process closely related to release and supply of nutrients,formation of greenhouse gases,and maintenance of soil quality.In incubation experiments and chemical analysis of soil samples of Udic Isohumisols,Udic Cambosols,Hapli-Stagnic Anthrosols No.1 and No.2,Fe-leach-Stagnic Anthrosols,Feaccumul-Stagnic Anthrosols gathered in East China,dynamics of soluble organic carbon content and soil organic carbon mineralization under different moisture treatments were investigated to determine difference in soluble organic carbon content between aerobic and submersion conditions as related to change in mineralization of soil organic carbon.Soluble organic C(SOC) was linearly and significantly related to wate-rsoil ratios ranging from 1:1 to 10:1,with different correlation coefficients(R²) in the soils(Udic Isohumisols 0.908^**,Udic Cambosols 0.973^**,Hapli-Stagnic Anthrosols No.20.933^**,Fe-leach-Stagnic An-hrosols 0.901^**,Fe-accumul-Stagnic Anthrosols 0.865^**).Cumulative SOC increased with the extracting time and SOC from a single event decreased with the frequency of the extraction.During the 8 weeks incubation,soluble organic C in the submergence treatments was 46% ~117% (p<0 05) for Hapl-i Stagnic Anthrosols No.1,112% ~285% (p<0 001) for Hapli-Stagnic Anthrosols No.2,and 21% ~73% (p<0 05) for Fe-accumul-Stagnic Anthrosols,higher than those in the aerobic treatments.In the first 3 weeks(for Hapli-Stagnic Anthrosols No.1) or 4 weeks(for Hapl-i Stagnic Anthrosols No.2) of incuba- tion,the daily mineralization of soil organic C was significantly different between moisture treatments(p<0 01),and tended to be similar thereafter;and the cumulative mineralization of soil organic C was significantly higher in the submergence treatment than in the aerobic treatment for the whole incubation period(p<0.01).Dynamics of the mineralization of soil organic C and trend of the change in content of soluble organic C tended to be similar,especially for Hapli-Stagnic Anthrosols No.2,which showed significant correlation coefficients(r) between soil organic C mineralization and soluble organic C content(0.942 in the aerobic treatment and 0.975 in the submergence treatment).Results also showed that difference in soil organic C mineralization(including daily and cumulative mineralization) between Hapli-Stagnic Anthrosols No.1 and No.2 was mainly related to their significant difference in content of soluble organic C,not the total soil organic C content.Significant increase in soluble organic C content as a result of submergence might be the main cause for a higher mineralization of soil organic C under the submersion condition than under the aerobic condition.