Drivers of nematode diversity in forest soils across climatic zones

Nematodes are the most abundant multi-cellular animals in soil, influencing key processes and functions in terrestrial ecosystems. Yet, little is known about the drivers of nematode abundance and diversity in forest soils across climatic zones. This is despite forests cover approximately 30% of the earth’s land surface, provide many crucial ecosystem services but strongly vary in hydrothermal conditions and associated ecosystem properties across climatic zones. Here, we collected nematode samples from 13 forests across a latitudinal gradient. We divided this gradient in temperate, warm-temperate, and tropical climatic zones and found that across the gradient, nematode abundance and diversity were mainly influenced by soil organic carbon. However, mean annual temperature and total soil phosphorus in temperate zones, soil pH in warm-temperate zones, and mean annual precipitation in tropical zones were more important in driving nematode alpha-diversity, biomass and abundance. Additionally, nematode beta-diversity was higher in temperate than in warm-temperate and tropical zones. Together, our findings demonstrate that the drivers of nematode diversity in forested ecosystems are affected by the spatial scale and climatic conditions considered. This implies that high resolution studies are needed to accurately predict how soil functions respond if climate conditions move beyond the coping range of soil organisms.