The relationship of plant diversity and several ecosystem functions strengthens over time. This suggests that the restructuring of biotic interactions in the process of a community’s assembly and the associated changes in function differ between species-rich and species-poor communities. An important component of these changes is the feedback between plant and soil community history. In this study, we examined the interactive effects of plant richness and community history on the trophic functions of the soil fauna community. We hypothesized that experimental removal of either soil or plant community history would diminish the positive effects of plant richness on the multitrophic functions of the soil food-web, compared to mature communities. We tested this hypothesis in a long-term grassland biodiversity experiment by comparing plots across three treatments (without plant history, without plant and soil history, controls with ~20 years of plot specific community history). We found that the relationship between plant richness and belowground multitrophic functionality is indeed stronger in communities with shared plant and soil community history. Our findings indicate that anthropogenic disturbance can impact the functioning of the soil community through the loss of plant species but also by preventing feedbacks that develop in the process of community assembly.

High-throughput sequencing (HTS) provides an efficient and cost-effective way to generate large amounts of sequence data. However, marker-based methods and the resulting datasets come with a range of challenges and disputes, including incomplete reference databases, controversial sequence similarity thresholds for delineating taxa, and downstream compositional data analysis. Here, we use HTS data from a soil nematode biodiversity experiment to address the following questions: (1) how the choice of reference database affects HTS data analysis, (2) whether the same ecological patterns are detected with ASV (100% similarity) versus classical OTU (97% similarity), and (3) how different data normalization methods affect the recovery of beta diversity patterns and identification of differentially abundant taxa. At this time, the SILVA database performed better than PR2, assigning more reads to family level and providing higher phylogenetic resolution. ASV- and OTU-based alpha and beta diversity of nematodes correlated closely, indicating that OTU-based studies represent useful reference points. For downstream data analyses, our results indicate that rarefaction-based methods are more vulnerable to missed findings, while clr-transformation based methods may overestimate tested effects. ANCOM-BC retains all data and accounts for uneven sampling fractions for each sample, suggesting that this is currently the optimal method to analyze compositional data. Overall, our study highlights the importance of comparing and selecting taxonomic reference databases before data analyses, and provides solid evidence for the similarity and comparability between OTU- and ASV-based nematode studies. Further, the results highlight the potential weakness of rarefaction-based and clr-transformation based methods. We recommend future studies use ASV and that both the taxonomic reference databases and normalization strategies are carefully tested and selected before analyzing the data.

Lignocellulose is a major component of plant biomass. Its decomposition is crucial for the terrestrial carbon cycle. Microorganisms are considered as primary decomposers and evidence increases that some invertebrates may also decompose lignocellulose. We investigated the taxonomic distribution and evolutionary origins of GH45 cellulases in a collection of soil invertebrate genomes and found that these genes are common in springtails and oribatid mites. Phylogenetic analysis revealed that cellulase genes were acquired early in the evolutionary history of these groups. Domain architectures and predicted 3D enzyme structures indicate that these cellulases are functional. Patterns of presence and absence of these genes across different lineages prompt further investigation into their evolutionary and ecological benefits. The ubiquity of cellulase genes suggests that soil invertebrates may play a role in lignocellulose decomposition, independently from microorganisms. Understanding the ecological and evolutionary implications might be crucial for understanding soil food webs and the carbon cycle.

Tropical soil microorganisms are major recyclers of biosphere organic carbon. However, the link of tropical microorganisms to the two primary carbon inputs (roots and litter) remains unclear. Here, we studied the effects of excluding living roots and litter on microorganisms in leaf litter and topsoil in rainforests and plantations in Sumatra, Indonesia. Unexpectedly, excluding living roots strongly decreased microbial biomass and basal respiration in litter but not in soil, indicating that tropical trees prioritize mining for nutrients in litter layer rather than mineral soil. Contrary to litter, soil microbial communities were predominantly influenced by long-term factors related to land-use history. Litter removal neither significantly affected microbial biomass nor community structure in soil, suggesting compartmentalized carbon processing between litter and soil. Our study sheds new light on fundamental-ecosystem processes in the tropics and calls for greater consideration of the litter layer and for including root-derived resources in global carbon cycling models.

Tropical rainforests around the world are rapidly converted into cash crop agricultural systems. The associated massive losses of plant and animal species lead to changes in arthropod food webs and the energy fluxes therein. These changes are poorly understood, in particular in the extremely biodiverse canopies of tropical ecosystems. Using canopy fogging followed by stable isotope and energy flux analyses, we show that land-use conversion from rainforest to rubber and oil palm plantations not only causes a drastic reduction in energy fluxes of up to 75%, but also shifts fluxes among trophic groups. While rainforest featured high levels of both herbivory and algae-microbivory, and a balanced ratio of herbivory to predation, relative fluxes were shifted towards predation in rubber and towards herbivory in oil palm plantations, indicating profound shifts in ecosystem functioning. Our results highlight that the ongoing loss of animal biodiversity and biomass in tropical canopies degrades animal-driven functions and restructures canopy food webs.

Earthworms modulate the carbon and nitrogen cycling in terrestrial ecosystems, their effect may be affected by deposited compounds due to human activity such as industrial emissions. However, studies investigating how deposited compounds affect the role of earthworms in carbon cycling such as litter decomposition are lacking, although they are important for understanding the influence of deposited compounds on ecosystems and the bioremediation by applying earthworms. For this, we performed a 365-day in situ litterbag decomposition experiment in a deciduous (Quercus variabilis) and coniferous (Pinus massoniana) forest in southeast China. We manipulated nitrogen (N), sodium (Na) and polycyclic aromatic hydrocarbon (PAH) deposited compounds during litter decomposition with and without earthworms (Eisenia fetida). After one year, N, Na and PAH compounds all slowed down litter mass loss, with the effects of Na being the strongest. By contrast, E. fetida generally increased litter mass loss and their positive effects were uniformly maintained irrespective of the type of deposited compounds. Further, the pathways earthworms increasing litter mass loss varied among the types of deposited compounds and forests. As indicated by structural equation modeling, earthworms maintained their positive effects and mitigated the negative effects of deposited compounds by directly increasing litter mass loss and indirectly increasing soil pH and microbial biomass. Overall, the results indicate that the acceleration of earthworms on litter mass loss is not affected by deposited compounds, with the pathways of earthworms increasing litter mass loss varying among the types of deposited compounds and forests. This suggests that the effects of atmospheric deposited compounds and earthworms on terrestrial ecosystem processes need to be taken into account because earthworms may cancel out the detrimental influence of deposited compounds on litter decomposition.

Belowground life is traditionally considered to rely on leaf litter as the main basal resource, whereas the importance of roots remains little understood, especially in the tropics. Here, we analysed the response of 30 soil animal groups to root trenching and litter removal in rainforest and plantations in Sumatra and found that roots are similarly important to soil fauna as litter. Trenching effects were stronger in soil than in litter with animal abundance being overall decreased by 42% in rainforest and by 30% in plantations. Litter removal little affected animals in soil, but decreased the total abundance by 60% both in rainforest and rubber plantations but not in oil palm plantations. Litter and root effects were explained either by the body size or vertical distribution of specific animal groups. Our findings highlight the importance of root-derived resources for soil animals and quantify principle carbon pathways in tropical soil food webs.

Urbanization-induced environmental changes such as habitat fragmentation impacts arthropod assemblages and food web-related ecosystem functions, such as nutrient cycling, carbon storage and energy fluxes. Yet, we lack insight into how arthropod food webs are structured along urban fragmentation gradients. Here, we investigated the community composition and food web structure of litter-dwelling arthropods along fragmentation gradients (green median strip, urban park, urban forest and natural forest). We found the density of litter-dwelling arthropods in median strip and urban park to be two to four times higher than in urban and natural forests, with, as indicated by literature-based stable isotope values, 67% - 68% of the individuals comprising primary consumers (trophic level I) in median strip and urban park. Urban forests, reserved for biodiversity conservation, hosted the least arthropod density, taxa richness, biomass and body mass, but were colonized by a high number of specialist arthropods, e.g. Archaeognatha and Isoptera. Food webs were most simple in urban forest, but more complex in median strip and urban parks, i.e. open fragments, with abundant primary and secondary consumers including decomposers. Chilopoda and Araneae formed the apex predators in fragments and mostly consumed other predators of trophic level III. The biomass of decomposed litter on the soil surface as major resource of the soil animal community significantly correlated positively with the density of arthropods of trophic levels I, III and IV. Supporting the dominance of bottom-up forces, the density of adjacent trophic levels consistently correlated positively. Overall, our results suggest that small size urban fragments maintain a diverse community of arthropods forming complex food webs and thereby may contribute to conserving biodiversity and providing important ecosystem functions.