Table_2_The Impact of Root-Derived Resources on Forest Soil Invertebrates Depends on Body Size and Trophic Position.xlsx

Forest soil food webs have been assumed to be fueled substantially by root-derived resources. However, until today the flux of root-derived resources into soil animals has been investigated virtually exclusively using isotope labeling experiments, whereas studies on the consequences of disrupting the flux of root-derived resources into the soil animal food web are scarce. We here investigated the importance of root-derived resources for a wide range of soil animals by interrupting the resource flux into the soil of different forest types in Central Europe using a trenching experiment. We recorded the abundance of soil animal taxa varying in body size (micro-, meso-, and macrofauna) 1 and 3 years after root trenching, and quantified changes in biomass, species composition, and trophic shift using stable isotopes and NLFA analysis. Among the microfauna groups studied (trophic groups of Nematoda) only the abundance of plant feeding nematodes showed a trend in being decreased by -58% due to root trenching. Major soil mesofauna groups, including Collembola and Oribatida, suffered to a similar extent from root trenching with their abundance and biomass being reduced by about 30–40%. The soil macrofauna groups studied (Diplopoda, Isopoda, Chilopoda, Araneae, Coleoptera) generally were only little affected by root trenching suggesting that they rely less on root-derived resources than micro- and in particular mesofauna. Notably, the community structure of micro-, meso-, and macrofauna was not affected by root trenching. Further, we observed trophic shifts only in 2 out of 10 investigated species with the shifts generally being only minor. The results indicate that soil animal communities are markedly resilient to deprivation of root-derived resources suggesting that links to root-derived resources are non-specific. However, this resilience appears to vary with body size, with mesofauna including both decomposers as well as predators being more sensitive to the deprivation of root-derived resources than microfauna (except for root feeders) and macrofauna. Overall, this suggests that body size constrains the channeling of energy through soil food webs, with root-derived resources in temperate forests being channeled predominantly via soil taxa of intermediate size, i.e., mesofauna.

森林土壤食物网曾被假定为在很大程度上依赖于根源资源。然而，直至今日，根源资源流入土壤动物的通量研究几乎完全依赖于同位素标记实验，而关于打断根源资源流入土壤动物食物网后果的研究却极为匮乏。本研究通过在中欧不同森林类型的土壤中实施挖掘实验，中断了根源资源通量，以探讨根源资源对于广泛土壤动物的重要性。我们记录了在根挖掘后1年和3年，不同体型（微生物群、中微生物群和大型微生物群）的土壤动物类群的丰度，并利用稳定同位素和NLFA分析量化了生物量、物种组成和营养级转移的变化。在研究的微生物群组（线虫的营养组）中，只有植物食性线虫的丰度显示出因根挖掘而降低的趋势，降低了58%。主要的土壤中微生物群组，包括弹尾目和螨目，其丰度和生物量因根挖掘而受到相似程度的损害，降低了约30-40%。研究的土壤大型微生物群组（双足纲、等足纲、蜈蚣目、蜘蛛目、鞘翅目）普遍仅受到轻微影响，这表明它们相较于微生物群和中微生物群，对根源资源的依赖性较小。值得注意的是，微生物群、中微生物群和大型微生物群的群落结构并未因根挖掘而受到影响。此外，我们仅在10种调查物种中的2种观察到营养级转移，且转移通常仅为微小。结果表明，土壤动物群落对于根源资源的剥夺表现出显著的弹性，表明与根源资源的联系不具有特异性。然而，这种弹性似乎与体型大小有关，中微生物群（包括分解者和捕食者）相较于微生物群（除根食性微生物外）和大型微生物群，对根源资源的剥夺更为敏感。总体而言，这表明体型大小限制了通过土壤食物网传递的能量通道，在温带森林中，根源资源主要通过中等大小的土壤生物群，即中微生物群进行传递。