Table_1_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.

森林土壤食物网一直被假设主要依赖于根源资源。然而，直至今日，根源资源流入土壤动物的研究几乎完全依赖于同位素标记实验，而对于中断根源资源流入土壤动物食物网所产生后果的研究却极为匮乏。本研究通过在中央欧洲不同森林类型的土壤中采用沟壑实验，中断了根源资源流入土壤的资源流，以探究根源资源对广泛土壤动物的重要性。我们在根沟挖掘后1年和3年，记录了不同体型（微型、中型和大型类群）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、物种组成和营养级的变化。在所研究的微型类群（线虫的营养群）中，仅植物食性线虫的丰度显示出因根沟挖掘而减少的趋势，减少了58%。主要土壤中型类群，包括跳甲和食尘螨，其丰度和生物量因根沟挖掘而受到相似程度的损害，减少约30-40%。所研究的土壤大型类群（双足纲、等足纲、蜈蚣纲、蜘蛛纲、鞘翅目）普遍仅受到轻微影响，这表明它们对根源资源的依赖程度低于微型和尤其中型类群。值得注意的是，微型、中型和大型类群的群落结构并未因根沟挖掘而受到影响。此外，我们在10个受调查物种中仅观察到2个物种的营养级发生转变，且这种转变通常仅是微小的。结果表明，土壤动物群落对根源资源的剥夺具有显著的可恢复性，这表明与根源资源的联系是非特异性的。然而，这种可恢复性似乎与体型大小有关，中型类群（包括分解者和捕食者）对根源资源剥夺的敏感性高于微型类群（除根食性动物）和大型类群。总体而言，这表明体型大小限制了能量通过土壤食物网的通道，温带森林中的根源资源主要通过中等大小的土壤类群，即中型类群进行能量传递。