中文关键词水稻土水分管理微生物生物量有机碳矿化酶活性 英文关键词paddy soilwater managementmicrobial biomassorganic carbon mineralizationenzyme activity

作者	单位	E-mail
刘琪	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125 中国科学院大学, 北京 100049	liuqi194@mails.ucas.ac.cn
李宇虹	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125	yuhong_li@isa.ac.cn
李哲	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125 中国科学院大学, 北京 100049
魏晓梦	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125
祝贞科	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125
吴金水	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125 中国科学院大学, 北京 100049
葛体达	中国科学院亚热带农业生态研究所, 亚热带农业生态过程重点实验室, 长沙 410125 中国科学院大学, 北京 100049

中文摘要 稻田土壤常处于频繁的干湿交替过程中，水分条件的改变不仅影响土壤理化性质，而且使土壤微生物群落结构和多样性发生改变，进而影响土壤有机碳矿化速率.然而，不同水分条件和土壤微生物生物量水平对土壤有机碳矿化过程的影响及其机制尚不明确.因此，本研究选取典型亚热带水稻土为研究对象，采用室内模拟培养试验，设置干湿交替和持续淹水这2个水分条件，并通过氯仿熏蒸方法减少土壤微生物生物量，从而获得微生物生物量碳含量高低两个水平的土壤，探讨水分条件和微生物生物量对水稻土有机碳矿化的影响机制.结果表明在培养前30 d，干湿交替处理处在不淹水状态，其CO₂累积排放量显著低于持续淹水处理；30 d后干湿交替处理进入淹水状态，在高微生物生物量碳含量土壤中，其CO₂累积排放量和持续淹水处理的差距逐渐减小，直至78 d无显著差异；在低微生物生物量碳含量土壤中，78 d时干湿交替处理的CO₂累积排放量仍显著低于持续淹水处理.低微生物生物量碳含量土壤在培养初期（前20 d）受其高可溶性有机碳（DOC）含量影响，CO₂排放速率可达高微生物生物量碳土壤的1.1~6.1倍；在培养后期（第45~78 d）土壤有机碳矿化速率达到稳定，高微生物生物量碳土壤的稳定矿化速率比低微生物生物量碳土壤高20%~30%.多元回归分析结果表明，土壤DOC含量的减少（ΔDOC）和Fe²⁺含量的增加（ΔFe²⁺）显著影响持续淹水条件下的CO₂累积排放量的变化值（ΔCO₂），但对干湿交替处理淹水阶段的CO₂累积排放量却无影响.相关分析结果表明，高微生物生物量碳土壤的CO₂日排放速率在干湿交替处理下与葡萄糖苷酶（BG）活性呈显著正相关，在持续淹水处理下与乙酰葡糖氨糖苷酶（NAG）和过氧化酶（PER）活性呈显著负相关；在低微生物生物量碳土壤中，CO₂日排放速率在持续淹水处理下与NAG活性呈负相关，在干湿交替处理下与酶活性无关.综上，干湿交替处理的CO₂累积排放量低于持续淹水处理，且该差异在低微生物生物量碳的土壤中显著；土壤微生物生物量大小会决定土壤有机碳稳定矿化速率水平；可溶性有机碳量和铁元素的还原量影响持续淹水条件下土壤的CO₂排放量；土壤水分条件会影响CO₂日排放速率及其关键生物酶因子.本研究为深入研究水稻土碳循环和固碳潜力提供数据和理论支持. 英文摘要 Paddy soil often undergoes frequent dry-wet alternation. The change in water status not only affects the physical and chemical properties of the soil, but also changes the structure and diversity of the soil microbial communities, which in turn determines the rate of soil organic carbon mineralization. However, the effects of different water conditions and soil microbial biomass levels on the process of soil organic carbon mineralization and its mechanisms are still unclear. Therefore, this study took typical subtropical paddy soil as the research object, applied a laboratory incubation experiment with two water treatments of dry-wet and continuous flooding, and reduced the soil microbial biomass through chloroform fumigation, thereby obtaining high and low soil microbial biomass carbon contents, to elucidate the influencing mechanisms of microbial biomass and water conditions on organic carbon mineralization in paddy soil. The results showed that during the first 30 d of incubation, the dry-wet treatment was in a non-flooded stage and its cumulative CO₂ emissions were significantly lower than those of the continuous flooded treatment. After 30 d, the dry-wet treatment entered the flooded stage. The difference in the cumulative CO₂ emissions of the soils with a high microbial biomass carbon content between the dry-wet and continuous flooding treatments gradually decreased, and there was no significant difference on day 78. In the soil with a low microbial biomass carbon content, the cumulative CO₂ emissions of the dry-wet treatment on day 78 was still significantly lower than that of the continuous flooded treatment. The soils with a low microbial biomass carbon content showed a faster CO₂ emission rate at the beginning of the incubation period (first 20 d), which was 1.1-6.1 times greater than that of the high microbial biomass carbon soils owing to their high soil dissolved organic carbon (DOC) content, and the CO₂ emission rate then gradually decreased until it was below that of the soil with a high microbial biomass carbon content. The soil organic carbon mineralization rate became stable later in the incubation period (days 45-78). The stable mineralization rate of the high microbial biomass carbon soil was 20%-30% higher than that of the low microbial biomass carbon soil. The multiple regression analysis results showed that the decrease in the soil DOC content (ΔDOC) and the increase in the Fe²⁺ content (ΔFe²⁺) significantly affected the change in cumulative CO₂ emissions (ΔCO₂) under continuous flooding conditions, but had no effect on ΔCO₂ during the flooding stage of the dry-wet treatment. The correlation analysis showed that the daily CO₂ emission rate of soils with high microbial biomass carbon was significantly positively correlated with glucosidase activity under dry-wet treatment and significantly negatively correlated with acetylglucosaminidase (NAG) and peroxidase activities under continuous flooding treatment. In the low microbial biomass carbon soils, the daily CO₂ emission rate of the continuous flooding treatment was negatively correlated with the NAG activity, but showed no correlation with enzyme activities under dry-wet management. In summary, the cumulative CO₂ emissions of dry-wet treatment were lower than those of continuous flooding treatment, and the difference was significant in soils with low microbial biomass carbon. The size of the soil microbial biomass determined the level of the stable soil organic carbon mineralization rate. The amount of soluble organic carbon and iron reduction affected the soil CO₂ emissions under continuous flooding conditions, and the soil water conditions affected the daily CO₂ emission rate and its key influencing enzymes. This study provides data and theoretical support for the carbon cycle and carbon sequestration potential in paddy soil.

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