蚯蚓对土壤温室气体排放的影响及机制研究进展
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中国科学院重点部署项目(KZZD-EW-TZ-16)、国家自然科学基金项目(41171047, 41371261)资助


Advancement in study on effect of earthworm on greenhouse gas emission in soil and its mechanism
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    摘要:

    土壤是温室气体的重要源和汇。蚯蚓是土壤物质循环的重要参与者,能够直接或间接影响土壤CO2、N2O和CH4等温室气体的产生和释放。蚯蚓呼吸产生的CO2,是土壤呼吸的重要组成部分;蚯蚓自身肠道、分泌液、消化物和排泄物等微环境促进反硝化过程释放N2O。蚯蚓还通过取食、掘穴、排泄等活动,改变土壤理化性质、微生物组成和活性及其他土壤动物的组成,影响地上植物生长,调节土壤分解、矿化、硝化、反硝化和甲烷生成及氧化等生态过程,间接影响土壤温室气体的排放。蚯蚓对土壤温室气体排放的影响逐渐受到重视,但目前研究仍以室内培养和单因子环境条件的模拟为主,缺少野外原位实验和多环境因子的交互实验研究。长期监测和同位素示踪技术,是深入探讨蚯蚓影响温室气体排放机制的重要手段。温室气体类型上,CO2和N2O是研究热点,CH4研究比较罕见。未来研究,应重视不同生态类群蚯蚓与土壤理化特征、微生物组成、其他类群土壤动物和地上植物间的交互作用,加强机制研究,并关注土壤污染环境下蚯蚓功能性状的变化;综合评价蚯蚓对土壤温室气体排放和土壤碳氮固定的影响,科学评估蚯蚓活动对土壤碳氮释放的促进或减缓作用。

    Abstract:

    Soil is an important source and sink, as well, of greenhouse gases (GHGs). Earthworms are a major component of the soil fauna, and a soil animal the highest in biomass in the soil. Being termed as soil ecosystem engineers, they play an crucial role in formation of soil physical-chemical properties and structure and in recycling of soil matter and nutrients through their feeding, burrowing and casting activities, thus directly or indirectly affecting the generation and emission of GHGs (CO2, N2O and CH4) in the soil. On one hand, the respiration of earthworm is an important part of soil respiration; in micro-environments, like guts, exudate, digesta and feces, anaerobic conditions, proper moisture content and rich C and N supply are favorable to growth and multiplication of denitrifying bacteria, thus greatly increasing biomass and activity of the bacteria, which in turn stimulates the emission of N2O during the process of denitrification (N2O 2.5~25 ng h-1 g-1 fresh earthworm), as is shown in recent studies. And N2O emission is higher from earthworm feces than from the soil in its surroundings. On the other hand, through feeding, burrowing and excreting, earthworms also cause changes in soil properties, composition and activity of soil microbes and some other ecological processes (e.g. decomposition, nitrification and denitrification), thus indirectly affecting GHGs emission. The activity of earthworms in the soil helps mix soil with plant residues and reshape soil pores and aggregates, thereby affecting soil moisture dynamics, aeration and content and availability of nutrients. Aerobic and anaerobic micro-environment within earthworm-made aggregates may also have some effect on decomposition and denitrification. Moreover, the macroaggregates formed by earthworms through their activities, in the long run, help C sequestration in microaggregates. Earthworms help blend plant residues with soil in their guts by feeding, thus expanding contact between microbes and organic matter, and alter composition and structure of the microbial community through their digestion and excretion processes. The interactions between earthworms and denitrifying and methanotrophic microbes cause formation of "drilosphere", where N2O emission increases and CH4 emission decreases. These effects are usually affected by soil moisture content, organic matter content and earthworm species. Based on their feeding and burrowing behaviors, earthworms are typically divided into three ecological groups: epigeic, endogeic and anecic species. Because of the differences in food accessibility and in distance the gases have to go through from the soil to the atmosphere, the three groups of earthworms differ sharply in ecological function, and the interactions between the groups make the effects on soil GHGs more complex. Besides, earthworm activities may also affect other soil fauna, such as mites, collembola, nematodes, isopods, enchytraeids, etc. in biomass and activity in their habitats. By the above-described indirect means, earthworms alter composition, structure and functions of the soil ecosystem. However, little is known about the effects of earthworm-plant interactions on GHGs balance in the soil. Besides, further researches are needed to fully understand interactions between different ecological groups of earthworms. To sum up, earthworms affect CO2, CH4 and N2O emissions mainly by regulating the ecological processes of carbon and nitrogen, such as decomposition, mineralization, nitrification, denitrification, methanogenesis and methanotrophy. Effects of earthworms on emission of GHGs have attracted more and more attention. Although much research has been done on the impacts of earthworms on soil CO2 and N2O emissions, little has been reported on CH4efflux. In view of the serious soil pollution problems, it is essential to unfold studies on changes in effects and potential role of earthworms in polluted soils. As for research techniques, current studies are still mainly based on short-term indoor incubation and simulation of one-factor environment. As the in-lab manipulated and simplified environments are far from good enough to reflect accurately the real conditions of the nature, it is urgent to start long-term in-situ field experiments and multi-environmental factor interaction experiments, because the functions of earthworm in the soil vary with the seasons; In addition, molecular and isotope tracing techniques have become available as effective tools for studies to expose biological and ecological mechanisms of earthworms’ effects on emissions of GHGs. It is essential, in future, to pay more attention to interactions of the different ecological groups of earthworms with soil properties, composition of soil microbes, other species of soil animals and plants growing on the surface of the soil, to intensify the study on mechanisms with stress on changes in earthworms’ function in polluted soils; to review comprehensively the effects of earthworms on emission of GHGs from the soil and carbon sequestration in the soil; to scientifically evaluate the effects of earthworm activities promoting or mitigating emissions of C and N from the soil.

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卢明珠,武海涛,吕宪国,管 强.蚯蚓对土壤温室气体排放的影响及机制研究进展[J].土壤学报,2015,52(6):1209-1225. DOI:10.11766/trxb201504170184 Lu Mingzhu, Wu Haitao, Lū Xianguo, Guan Qiang. Advancement in study on effect of earthworm on greenhouse gas emission in soil and its mechanism[J]. Acta Pedologica Sinica,2015,52(6):1209-1225.

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  • 收稿日期:2015-04-17
  • 最后修改日期:2015-07-01
  • 录用日期:2015-08-21
  • 在线发布日期: 2015-08-31
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