Data from: Aboveground mammal and invertebrate exclusions cause consistent changes in soil food webs of two subalpine grassland types, but mechanisms are system-specific

Ungulates, smaller mammals, and invertebrates can each affect soil biota through their influence on vegetation and soil characteristics. However, direct and indirect effects of the aboveground biota on soil food webs remain to be unraveled. We assessed effects of progressively excluding aboveground large-, medium- and small-sized mammals as well as invertebrates on soil nematode diversity and feeding type abundances in two subalpine grassland types: short- and tall-grass vegetation. We explored pathways that link exclusions of aboveground biota to nematode feeding type abundances via changes in plants, soil environment, soil microbial biomass, and soil nutrients. In both vegetation types, exclusions caused a similar shift toward higher abundance of all nematode feeding types, except plant feeders, lower Shannon diversity, and lower evenness. These effects were strongest when small mammals, or both small mammals and invertebrates were excluded in addition to excluding larger mammals. Exclusions resulted in a changed abiotic soil environment that only affected nematodes in the short-grass vegetation. In each vegetation type, exclusion effects on nematode abundances were mediated by different drivers related to plant quantity and quality. In the short-grass vegetation, not all exclusion effects on omni–carnivorous nematodes were mediated by the abundance of lower trophic level nematodes, suggesting that omni–carnivores also depended on other prey than nematodes. We conclude that small aboveground herbivores have major impacts on the soil food web of subalpine short- and tall-grass ecosystems. Excluding aboveground animals caused similar shifts in soil nematode assemblages in both subalpine vegetation types, however, mechanisms turned out to be system-specific.有蹄类动物、小型哺乳类及无脊椎动物均可通过影响植被与土壤特征作用于土壤生物群落（soil biota）。然而，地表生物对土壤食物网（soil food webs）的直接与间接效应仍有待阐明。本研究针对两类亚高山草地（subalpine grassland）——短草植被与高草植被，探究了逐步排除地表大型、中型、小型哺乳类及无脊椎动物对土壤线虫（soil nematode）多样性及食性类群丰度的影响。本研究还通过植被、土壤环境、土壤微生物生物量及土壤养分的变化，探索了地表生物排除操作与线虫食性类群丰度之间的关联路径。在两类植被类型中，除植食性线虫外，排除操作均促使所有线虫食性类群的丰度呈现相似的上升趋势，同时香农多样性指数（Shannon diversity）与均匀度（evenness）均有所降低。当仅排除大型哺乳类、或同时排除小型哺乳类与无脊椎动物时，上述效应最为显著。排除操作改变了非生物土壤环境，且该变化仅对短草植被中的线虫产生影响。在每一类植被类型中，排除操作对线虫丰度的影响均由与植被数量和质量相关的不同驱动因子所介导。在短草植被中，并非所有排除操作对杂食-捕食性线虫（omni–carnivorous nematodes）的效应均由低营养级（trophic level）线虫的丰度所介导，这表明杂食-捕食性线虫的猎物除线虫外还依赖其他生物。我们得出结论：地表小型植食动物对亚高山短草与高草生态系统的土壤食物网具有显著影响。尽管排除地表动物会使两类亚高山植被群落的土壤线虫类群组成产生相似的变化，但其背后的机制却因生态系统类型而异。