Soil nematodes are important contributors to soil biodiversity. Nonetheless, the distribution patterns and environmental drivers of soil nematode communities are poorly understood, especially at the large scale, where multiple environmental variables covary. We collected 520 soil samples from 104 sites representing alpine meadow and steppe ecosystems. First, we explored the soil nematode community characteristics and compared community patterns between the ecosystems. Then, we examined the contributions of aboveground and belowground factors on these patterns. The genus richness and abundance of nematodes on the Tibetan Plateau are lower than other alpine ecosystems, but are comparable to desert or polar ecosystems. Alpine meadows supported a higher nematode abundance and genus richness than alpine steppes; bacterial-based energy channels were pre-dominant in both the ecosystems. Soil factors explained the most variation in the soil nematode community composition in the alpine meadows, while plant factors were as essential as soil factors in the alpine steppes. Unexpectedly, the climate variables barely impacted the nematode communities. This is the first study to explore the spatial patterns of soil nematode compositions on the Tibetan Plateau, and we found that the contributions of climate, plants, and soil properties on soil nematodes community were essentially different from the previous knowledge for well-studied plant and animal communities.

Background and aims: Extreme environments (polar, alpine, arid) are frontiers of global change, where the interaction between plants and soil biota dictates ecosystem resilience. Soil nematodes are critical components of the soil food web, mediating nutrient cycling. This review synthesizes current understanding of nematode ecology across these systems, focusing on adaptive strategies, biogeographic patterns, and climate change responses. Scope: We combine research from around the world on soil nematodes from polar, alpine, and dry areas. We examine their adaptive strategies, what causes their community structure, and how they respond to climate change. Results: Soil nematode survival is underpinned by convergent adaptations, notably cryptobiosis and opportunistic life histories. While liquid water availability is a universal constraint, biogeographical patterns are shaped by system-specific drivers: temperature thresholds in cold environments and moisture pulses in deserts. Our synthesis reveals that local soil properties and, where present, vegetation patches (e.g., biocrusts, plant rhizospheres) create crucial micro-refugia, often overriding macroclimatic controls. Climate change impacts are primarily indirect; for instance, warming affects nematodes by altering permafrost stability and meltwater regimes in polar regions or by inducing uphill shifts in plant communities in alpine zones, creating mismatches between migrating nematodes and soil development. Conclusions: Soil nematode communities in extreme environments are highly sensitive indicators of climate change, responding to shifts in both abiotic and biotic conditions. Understanding their adaptive limitations and the response pathways is critical for predicting the future of nutrient cycling and the stability of communities in Earth's most vulnerable ecosystems. Future research should focus on the multi-faceted interactions between plants, microbes, and nematodes under combined global change stressors.