The ‘home-field advantage’ (HFA) hypothesis predicts that litter decomposition is accelerated in its home environment (i.e. in conspecific soil). Soil organisms play a key role in driving such HFA effects. Soil biota have a large range of body sizes, referred to as size fractions, which may influence their roles in the decomposition process and in the generation of HFA effects. However, how HFA effects depend on the different size fractions of the soil biotic community is unknown. We conducted a microcosm decomposition experiment to examine how size fractions of the soil biotic community affected litter decomposition and HFA effects. In a semi-natural grassland in the Netherlands, we collected leaf litter and soil from two abundant forbs: Tanacetum vulgare and Jacobaea vulgaris. Watery extracts of the soils were sieved through differently-meshed sieves (ranging from 850 μm to 6 μm) to obtain soil communities of different size fractions. Microcosms were inoculated with these different size fractions of the soil biotic community and we examined their effects on microbial composition, litter mass loss and HFA effects. Three months after inoculation, the diversity of the fungal community in the inoculated pots decreased with decreasing size fractions of the soil biotic community. Similarly, litter mass loss also decreased with decreasing soil biotic community size. In contrast, the HFA effect increased with decreasing size fractions of the soil biotic community, but these differences disappeared after six months of decomposition. Our results indicate that soil microorganisms, mainly the smallest size fractions, are specialized to decompose specific resources and thus promote HFA effects, but that their effect is only apparent during specific stages of litter decomposition.

“家庭田间优势”（HFA）假说预测，垃圾在其家庭环境中（即在特定土壤中）会加速分解。土壤生物在驱动此类HFA效应中起关键作用。土壤生物区系的人体大小范围很大，称为大小分数，这可能会影响它们在分解过程和HFA效应产生中的作用。但是，HFA的作用如何取决于土壤生物群落的不同大小比例尚不清楚。我们进行了微观分解实验，以研究土壤生物群落的大小分数如何影响凋落物分解和HFA效应。在荷兰的半天然草原上，我们从两个丰富的小叶草（艾菊和寻常雅各布）中收集了凋落物和土壤。将土壤的含水提取物通过筛网不同的筛网（范围从850μm到6μm）进行筛分，以获得大小不同的土壤群落。用这些不同大小的土壤生物群落接种缩微菌，我们检查了它们对微生物组成，凋落物质量损失和HFA效应的影响。接种后三个月，接种盆中真菌群落的多样性随着土壤生物群落大小分数的降低而降低。同样，凋落物质量损失也随着土壤生物群落规模的减小而减少。相反，HFA效应随着土壤生物群落大小分数的减小而增加，但这些差异在分解六个月后消失了。我们的结果表明，土壤微生物（主要是尺寸最小的部分）