Exploring the influence of natural features on soil mesofaunal communities in agricultural landscapes through DNA metabarcoding

Soil mesofauna critically support organic matter decomposition and nutrient cycling, as well as regulating pests and diseases. Agricultural activities can physically and chemically influence soil mesofauna community structure, thereby impacting the ecosystem services these mesofauna provide. Conserving natural features in agricultural environments is well known to support biodiversity and associated ecosystem services, yet soil mesofauna communities and their functions in such features require further study. We sampled the soil mesofaunal communities (focusing on Acari (mites) and Collembola (springtails)) in mixed-use, but agriculturally-dominated landscapes in southeastern Ontario, Canada. Semi-natural features were represented by drainage ditch banks with varying amounts of woody vegetation to different kinds of forested blocks. Specimens were extracted using Berlese funnels, and COI metabarcoding was conducted on the bulk specimen samples. A total of 585 operational taxonomic units (OTUs; a proxy for species) were identifiable based on DNA sequences, 390 of which belonged to either Acari (273) or Collembola (117); however, it was rarely possible to identify specimens to species-level. Mesofaunal richness did not differ among habitat types but community composition varied between low woody-vegetation drainage bank sites and forested blocks. Maintaining heterogeneous natural and semi-natural features appears to increase the overall diversity of mesofauna on the landscape, and even small forest patches support forest-associated soil biodiversity in this agricultural region.

土壤中型动物群（Soil mesofauna）在有机质分解、养分循环及病虫害调控中发挥关键支撑作用。农业活动可通过物理与化学途径影响土壤中型动物群的群落结构，进而干扰此类类群所提供的生态系统服务功能。现有研究表明，在农业环境中保留自然生境有助于维持生物多样性及其配套的生态系统服务，但针对此类生境中土壤中型动物群群落及其功能的研究仍有待深化。本研究在加拿大安大略省东南部以农业为主的混合利用景观中开展土壤中型动物群群落采样，重点关注蜱螨亚纲（Acari）与弹尾纲（Collembola，俗称跳虫）类群。半自然生境涵盖木本植被覆盖度各异的排水沟岸，以及不同类型的林地块。标本采用贝尔莱泽漏斗（Berlese funnels）进行分离提取，随后对混合标本样本开展COI元条形码（COI metabarcoding）测序。基于DNA序列共鉴定出585个操作分类单元（operational taxonomic units，OTUs，物种替代指示指标），其中390个隶属于蜱螨亚纲（273个）或弹尾纲（117个）；但绝大多数标本难以鉴定至物种水平。不同生境类型的中型动物群丰富度无显著差异，但群落组成在低木本植被覆盖的排水沟岸与林地块之间存在显著分化。研究显示，维持异质性的自然与半自然生境可提升该农业景观中土壤中型动物群的整体多样性，即便小型森林斑块也能为本区域农业景观中的森林关联土壤生物多样性提供支撑。