赤子爱胜蚓(Eisenia fetida)对秸秆施入后土壤有机碳和微生物的影响

Effects of Eisenia fetida Inoculation on Soil Organic Carbon and Soil Microorganisms Under Rice Straw Application

蚯蚓能够通过自身生命活动和对土著土壤生物的调控作用而直接或间接影响土壤活性有机碳的变化。为探索蚯蚓影响土壤有机碳变化的机理,在混入水稻秸秆的灭菌/未灭菌土壤中接种蚯蚓(Eisenia fetida),以不接种蚯蚓的处理为对照,比较30 d微宇宙培养后不同处理土壤有机碳含量及土壤微生物群落结构的变化。结果显示,接种蚯蚓增加了土壤微生物量碳(MBC)和CO2累积排放量,但仅在灭菌土壤中存在显著性差异。接种蚯蚓对土壤总有机碳(TOC)、活性有机碳(LOC)和可溶性有机碳(DOC)的影响则因土壤是否灭菌而异。末端限制性片段长度多样性(T-RFLP)分析显示,在灭菌土壤中接种蚯蚓获得了更多的末端片段(TRFs),而在未灭菌土壤中蚯蚓的存在并未明显改变TRFs的数量,且接种蚯蚓与无蚯蚓的处理共享了近50%的TRFs。冗余分析(RDA)显示土壤细菌群落结构因蚯蚓是否存在而不同,但仅在灭菌土壤中接种蚯蚓的处理同时与LOC、DOC、MBC和CO2累积排放量呈较好的正相关关系。因此认为,在该实验的灭菌土壤中,来源于蚯蚓肠道的微生物可能通过快速繁殖并成为优势种进而影响土壤有机碳的变化,但这一作用在未灭菌土壤中则有可能因为土壤土著微生物的竞争作用而被削弱。

Earthworms influence soil organic carbon dynamics directly through their biological activities and indirectly via modified indige-nous soil organisms. In this microcosm study, un-sterilized and sterilized soils(indigenous organism′s free soil)were used to compare the differences in soil organic carbon and microorganisms induced by earthworm(Eisenia fetida)over the 30-day study period. Soils inoculated with earthworms increased cumulative CO2 emissions and microbial biomass carbon compared with no earthworm soil, while significant differences were observed only in the sterilized soil. The effects of earthworms on soil total organic carbon, labile organic carbon and dissolved organic carbon varied depending on sterilization. The presence of earthworm decreased soil labile organic carbon from 5.39 g·kg-1to 5.06 g·kg-1in un-sterilized soil, while significantly increased from 5.62 g·kg-1to 6.45 g·kg-1in sterilized soil. Meanwhile, terminal restriction fragments(TRFs)were more diverse in sterilized soil with earthworms than one without earthworm, while no obvious changes were found in unsterilized soils, in which the presence and absence of earthworms shared almost 50% of TRFs. Redundancy analysis showed that there were no obvious clustering phenomena among all treatments, indicating the changes in bacterial community structure by earthworm inoculation.Nevertheless, earthworm inoculation in sterilized soil was correlated positively with cumulative CO2 emissions, microbial biomass carbon, labile organic carbon and dissolved organic carbon. In conclusion, earthworms may change soil organic carbon by stimulating and changing soil bacterial community by gut-associated bacteria in the sterilized soil, which may be diminished due to the competition of indigenous soil microorganisms in un-sterilized soil.