Enhanced plant litter impact nematode communities and carbon use efficiency in a mixed forest

Rising temperatures and higher atmospheric CO2 levels can potentially increase plant photosynthesis and boost forest productivity, in turn spurring litter inputs to soils on a global scale. Understanding the feedback loops between increased litter inputs and soil biota activity will allow better prediction of organic matter and carbon (C) cycling in terrestrial ecosystems. Nematodes represent the full spectrum of trophic groups within the soil biota. Accordingly, we studied the link between nematode metabolic activities and plant litter input. For this, different litter input levels were manipulated in a temperate forest, including control zones, natural litter input zones, and zones with double, triple, and quadruple amounts of natural litter input. Soil top layers (0-10 cm) were then collected to study the responses of nematode communities. Increased litter input positively influenced the abundance and diversity of nematodes, except for plant-parasitic species. Higher litter input levels led to an enhancement in the ratio of bacterivores to the total of bacterivores and fungivores. More litter increased the K/r strategist ratio among bacterivores, and the corresponding nematode metabolic footprints. More litter also stimulated nematode production and respiration components and improved the carbon use efficiency of bacterivores. Moreover, the structural equation modeling revealed the crucial role of bacterivores in influencing soil organic C under increased litter input. In conclusion, our study shows that increased plant aboveground litter input modifies the taxonomic and functional communities of soil nematodes, ultimately regulating the carbon cycle in forest soils.