土壤动物多样性及其生态功能

土壤无脊椎动物生物量通常小于土壤生物总生物量的10%,但它们种类丰富,取食行为及生活史策略多种多样,且土壤动物之间,土壤动物与微生物之间存在着复杂的相互作用关系。土壤动物的生态功能主要通过取食作用(trophic effect)和非取食作用(non-trophic effect)来实现。原生动物数量大、周转快,故原生动物本身的代谢活动(即取食作用)对碳氮矿化的贡献可以接近甚至超过细菌的贡献;然而大多数中小型土壤动物的本身代谢过程对碳氮矿化的贡献远低于土壤微生物,但它们可以通过取食作用来调节微生物进而影响碳氮的矿化。大型节肢动物中的蜘蛛和地表甲虫等捕食者经常活跃于地表,它们常常会通过级联效应对土壤生态系统产生重要的影响。蚯蚓、白蚁等大型土壤动物除可以通过取食作用以外,还可以通过非取食作用调控土壤微生物,进而显著影响土壤碳氮过程。土壤动物取食行为的多样性和复杂的非营养关系的存在造就了多维度的土壤食物网,给土壤动物的生态功能研究带来了巨大的挑战。介绍了土壤动物的多样性及主要的生态功能,并对研究的热点和前沿问题进行了探讨,以期引起关于土壤动物多样性及其生态功能的深入思考。

Diversity and function of soil fauna

Soil invertebrate biomass accounts for less than 10% of the total soil biomass, but it is characterized by abundant species, and diverse feeding behavior and life strategies, which can result in complex interactions among soil faunal groups and soil microbes. Soil fauna contribute primarily to ecosystem functioning through trophic and/or non-trophic effects. Soil protozoa, the most abundant faunal group with the highest turnover rate among soil fauna, equivalent to or even higher than that of soil bacteria, contribute to carbon and nitrogen mineralization via their own metabolic processes. In contrast, other soil faunal groups have much less impact on carbon and nitrogen mineralization, as compared to soil microbes. Most micro- and/or meso-faunal groups can regulate soil microbial processes directly by feeding on detritus and microbes, and indirectly affect soil carbon and nitrogen processes. In addition, predators such as spiders and ground beetles can affect soil ecosystems via the trophic cascade effects of predators. However, macrofauna such as earthworms and termites may regulate soil microbes, and thus alter soil carbon and nitrogen processes considerably by non-trophic effects. The diverse feeding strategies of soil fauna and the complex non-trophic relationships establish multi-dimensional soil food webs, and these pose enormous challenges to the studies of soil faunal function. Here, we outline briefly the diversity and ecosystem functioning of soil fauna, and highlight some frontiers and hot issues to inspire in-depth understanding of interactions between the diversity and function of soil fauna.