Scale-dependent dispersal limitation in soil nematode community assembly in sorghum agroecosystems

Soil nematodes, which are the most prevalent and widespread group of soil fauna, play a crucial role in maintaining soil health and supporting agricultural productivity. Despite their importance, the mechanisms underlying the assembly of soil nematode communities in agricultural ecosystems, particularly how these mechanisms vary across different spatial scales, remain poorly understood. In this study, we examined the community assembly processes of soil nematodes across a geographical span of 4,138 km, covering multiple spatial scales within sorghum agricultural ecosystems. Our results reveal that, with increasing spatial scale, the contribution of stochastic processes gradually decreases, whereas deterministic factors become increasingly important. The iCAMP model indicates that dispersal limitation (78.88%) predominantly drives the community assembly mechanisms of soil nematodes. The importance of dispersal limitation and heterogeneous selection significantly increases, while the importance of homogeneous selection significantly decreases with increasing spatial scale. Additionally, we identified soil nitrogen, total phosphorus, and precipitation as key drivers influencing the variability in these assembly processes across spatial scales. This study provides novel insights into the spatial dynamics and scale-dependent community assembly of soil nematodes, with important implications for predicting changes in their ecosystem functions in response to future environmental changes.