好气和淹水处理间苏南水稻土有机碳矿化量差异的变化特征

Characteristics of Organic C Mineralization Under Aerobic and Submerged Conditions in Paddy Soils of Southern Jiangsu Province

【目的】探讨好气与淹水处理间水稻土有机碳矿化量差异的变化特征。【方法】采集江苏省常熟市全市范围的代表性水稻土样品并布置室内好气与淹水处理的恒温培育试验,观测土壤有机碳矿化的动态过程及矿化量变化,比较分析不同水分状况处理的土壤有机碳矿化量差异及形成机制。【结果】培养过程中不同水分状况处理下土壤有机碳日均矿化量变化趋势有显著差异,好气处理下培养前期迅速下降,而淹水处理下则迅速升高,并均在培养10d后趋于稳定;好气与淹水处理间有机碳日均矿化量差异主要表现在培养前期,随培养时间延长而不断减小,以致培养后期差异不明显。好气处理下土壤的基础呼吸强度、有机碳日均矿化量和累计矿化量分别是淹水处理的2.26—19.11、0.96—2.41、0.96—2.41倍。统计分析表明,土壤中微生物生物量碳、氮含量越高则好气与淹水处理间呼吸强度差异越大,而若土壤中微生物生物量氮、水溶性有机碳含量越高则好气与淹水处理间土壤有机碳日均矿化量差异越大。【结论】淹水处理造成土壤微生物活性降低是导致土壤呼吸强度下降的主要原因,而在整个培养过程中土壤有机碳矿化量的变化还与水溶性有机碳含量有关。

[Objective] Moisture regime plays a crucial role in the mineralization of soil organic carbon （SOC）. In this paper, the differences in SOC mineralization under aerobic and submerged conditions of paddy soils were studied. [Method] With incubation under aerobic and submerged conditions in laboratory, the dynamics of SOC mineralization in typical paddy soils of Changshu, Jiangsu Province, was investigated. [Result] The daily mineralization of SOC under different moisture regimes was significantly different in the whole incubation period. The daily mineralization of soil organic carbon decreased quickly at the beginning of the incubation under aerobic condition, but increased rapidly under submerged condition, and both kept constant after 10 days＇ incubation. The differences in SOC mineralization were found to be mainly at the beginning period of the incubation and decreased along with the incubation time. Thus the difference was not significantly different at the later incubation time. The respiration intensity, daily and cumulative mineralization of SOC under aerobic condition were 2.26-19.11, 0.96-2.41, and 0.96-2.41 times those under submerged condition, respectively. Statistic analyses showed that the higher the contents of microbial biomass carbon and nitrogen, the more significant difference in respiration intensity between aerobic and submerged conditions, but the higher the contents of microbial biomass nitrogen and dissolved organic carbon, the more significant difference in daily mineralization of SOC between the two conditions. [Conclusion] The decrease in soil microbe activity under submerged condition was the main reason leading to the decrease in respiration intensity, but the decrease in SOC mineralization was also correlated with the changes in dissolved organic carbon over the whole incubation period.