Understanding ecological and evolutionary mechanisms that drive biodiversity patterns is important for comprehending biodiversity. Despite being critically important to the functioning of ecosystems, the mechanisms driving belowground biodiversity are little understood. We here investigated the radiation and trait diversity of soil oribatid mites from two mountain ranges, i.e. the Alps in Austria and Changbai Mountain in China, at similar latitude in the temperate zone differing in orogenesis and exposed to different climates. We collected and sequenced soil oribatid mites from forests at 950 to 1700 m at each mountain and embedded them into the chronogram of species from temperate Eurasia. We investigated the phylogenetic age of oribatid mites and compared the node age of species with the mountain uplift time of the Alps and Changbai Mountain. We then inspected trophic variation, geographical range size and reproductive mode, and identified traits that promote oribatid mite survival and evolution in montane forest ecosystems. We found that oribatid mites on Changbai Mountain are phylogenetically older than species in the Alps. All species on Changbai Mountain evolved long before the mountain uplift, but some species in the Alps evolved after the orogenesis. On Changbai Mountain more species possess broader trophic variation, have larger geographical range sizes and more often reproduce via parthenogenesis compared to species from the Alps. Species on Changbai Mountain survived the mountain uplift or colonized the mountain thereafter supporting the view that generalistic traits promote survival and evolution in phylogenetically old soil animal species. Collectively, our findings highlight that combining species traits and phylogeny allow deeper insight into the evolutionary forces shaping soil biodiversity in montane ecosystems.

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.

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.