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为了进一步认识水稻秸秆还田后土壤有机碳固定机制,以浙江两种典型水稻土淡涂泥、青紫泥为研究对象,并以不加秸秆为对照,研究秸秆施用下土壤溶解性有机碳(Dissolved Organic Carbon,DOC)含量以及CO_2产生速率的动态变化,以及秸秆分解产生DOC在土壤中的吸附作用。结果表明,添加秸杆显著增加了土壤CO_2排放,总矿化碳量表现为10%>5%>2%>CK;土壤CO_2产生速率的变化与DOC含量变化具有高度一致性,都表现为先快速上升-急剧下降-缓慢下降-趋于稳定的变化模式,两者呈显著正相关(P<0.01),但在石英砂处理中两者则无明显相关性。DOC吸附实验表明随着秸秆分解时间延长,所产生的DOC在土壤中的吸附作用增强。pH和本底DOC较低的青紫泥对DOC具有更强的吸附作用,其CO_2排放速率和总矿化碳量均显著低于淡涂泥,青紫泥更有利于秸秆还田有机碳的保留和稳定。该结果表明秸秆分解前期产生DOC主要以CO_2形式释放,分解后期产生DOC更倾向于土壤有机碳固定,增加土壤对DOC的吸附作用有利于土壤固碳。
In order to further understand the mechanism of soil organic carbon fixation after returning rice straw to the soil, two typical paddy soils of Zhejiang Province were used to study the effect of soil dissolved organic carbon (DOC) Organic Carbon, DOC) content and CO 2 production rate, as well as the adsorption of DOC in soil by straw decomposition. The results showed that adding straw significantly increased soil CO 2 emission, and total carbon mineralization showed 10%> 5%> 2%> CK. The change of soil CO 2 production rate was highly consistent with that of DOC content (P <0.01). However, there was no significant correlation between them in quartz sand treatment. DOC adsorption experiments showed that as the decomposition time of straw was extended, the adsorption of DOC produced in the soil was enhanced. Purple soil with lower pH and DOC had stronger adsorption to DOC, and its CO 2 emission rate and total carbon mineralization were significantly lower than those of lightly-coated mud and brucite more conducive to the retention of organic carbon in straw-returning stable. The results showed that the DOC produced during the early stage of straw decomposition was mainly released as CO 2, and the DOC produced during the later stage of decomposition was more likely to be fixed in the soil organic carbon. Increasing the adsorption of DOC to the soil was beneficial to soil carbon sequestration.