两种代表性蚯蚓对设施菜地土壤微生物群落结构及理化性质的影响

Impacts of two typical earthworms on soil microbial community structure and physicochemical properties in a greenhouse vegetable field

不同生态型蚯蚓的取食偏好和生境有所差异,因此蚯蚓的生态型差异可能关乎其对土壤性质的不同影响;有关不同生态型蚯蚓对土壤性质尤其是微生物学性质影响的研究有助于了解蚯蚓生态功能的作用机制。在野外调控试验的第4年采集土壤,研究了牛粪混施和表施处理下内层种威廉腔环蚓(Metaphire guillelmi)和表层种赤子爱胜蚓(Eisenia foetida)对设施菜地土壤微生物群落结构和主要理化性质的影响。结果表明,土壤微生物群落结构同时受到蚯蚓种类和牛粪施用方式的影响。牛粪表施时,两种蚯蚓均显著降低了菌根真菌、真菌生物量和原生动物生物量(P<0.05);牛粪混施时,不同蚯蚓的影响有所差异,威廉腔环蚓明显增加了菌根真菌、真菌生物量和放线菌生物量,而赤子爱胜蚓的作用不明显。此外,两种蚯蚓均提高了土壤孔隙度、团聚体稳定性和土壤p H、矿质氮以及微生物生物量碳氮水平,但提高幅度取决于蚯蚓种类和牛粪施用方式。冗余分析表明蚯蚓影响下土壤微生物群落结构的变化与团聚体稳定性、p H、速效磷、矿质氮呈正相关,而与土壤容重呈负相关。

Earthworms are considered one of the most important soil ecosystem engineers. Earthworms play critical roles in soil functioning through their burrowing, feeding, and casting activities. There are distinct ecological strategies （i.e., food selection, ingestion, assimilation, and habitat preference ） for different earthworm ecotypes. Consequently, different earthworm eeotypes would have different effects on soil properties. Understanding the impacts of different earthworms on soil microbial communities would increase our mechanistic understanding of the role of earthworms in ecosystem services. Several studies have shown that earthworms facilitate the translocation of fresh residues into soil and create suitable habitat （casts, middens and burrows ） for other soil organisms. Moreover, the interaction of earthworm feeding strategies and organic amendment could profoundly modulate soil properties and microbial community structure. However, there is a knowledge gap in this respect. In particular, few studies have been conducted under field conditions. To understand the long-term impact of earthworms and manure on soil microbial community structure, a tomato-spinach rotation experiment was initiated in 2009. Based on the soil collected during the fourth year following the set-up of the field experiment, the effects of two typical earthworms （i.e., endogeic Metaphire guillelmi and epigeic Eiseniafoetida） and two manure application treatments （i.e., surface mulch and incorporation into the soil） on soil microbial community were investigated. The native endogeic species, Metaphire guillelmi, lives in the upper soil layers and primarily consumes soil mineral particles rich in organic matter, whereas E. foetida, a well-known epigeic species, resides mainly in the upper organic layers and feeds on litter materials. Our results demonstrated that soil microbial community structure was significantly affected by earthworm species and the method of manure application. With manure application at the soil surface, earthworms could significantly decrease mycorrhizal fungi, fungi biomass and protozoa biomass independent of earthworm type （P 〈 O. 05 ）. When manure was incorporated into the soil, M. guillelmi significantly increased mycorrhizal fungi, fungi biomass and actinomyces biomass, although the effect of E. foetida was not significant. Regardless of type, earthworms significantly increased soil porosity, soil aggregate stability represented by mean weight diameter and pH, soil mineral nitrogen, available phosphorus, as well as microbial biomass carbon and nitrogen content. In addition, the extent of increase depended on earthworm ecotype and the method of manure application. Redundancy analysis showed that earthworm-mediated microbial community structure was positively correlated with soil aggregate stability as expressed by mean weight diameter, pH, and available phosphorus content, whereas it was negatively correlated with soil bulk density.