Elevational Gradients of Soil Nematode Communities in Subtropical Forest Ecosystems

Soil biodiversity plays a critical role in supporting multiple ecosystem functions. As some of the most diverse and abundant metazoans on the Earth, soil nematode communities exhibit changes along environmental gradients, but the ways in which the abundance and diversity of nematode communities vary along elevational gradients remain poorly understood. Taking advantage of an investigation on Huangshan Mountain, Southeast China, with elevation ranging from 500 to 1200 m, we assessed the abundance and diversity of soil nematodes, as well as the soil physicochemical properties, across subtropical forest ecosystems. Nematode communities were analyzed at the genus level, and the α-diversity was calculated as the genus richness, while the β-diversity was based on the Bray–Curtis dissimilarity. The results showed that, among the top 20 nematode genera ranked by absolute abundance, most genera, such as Eucephalobus, Prismatolaimus, Filenchus, and Rotylenchulus, reached their peak abundance at the highest elevation (1000 m). Additionally, the abundances of Oriverutus, Tylenchus, Criconema, and Tripyla exhibited a positive correlation with the elevation. Moreover, the abundance and α-diversity of the total nematodes and each trophic group of nematodes increased linearly with the elevation, likely due to increased soil moisture at higher elevation. In contrast, the β-diversity of the total nematodes, bacterivores, and herbivores decreased with increasing elevation, indicating the importance of stochastic processes in shaping community assembly at high altitudes. This pattern suggests that as the elevation increases, the nematode communities become more homogeneous in structure. Taken together, our study’s findings demonstrate the divergent responses of nematodes’ α- and β-diversity to an elevation gradient, highlighting the importance of the soil nematode diversity in maintaining ecosystem functions such as nutrient cycling and food web stability in mountainous regions. These results emphasize the need to incorporate the below-ground biodiversity into conservation strategies, particularly in the face of environmental changes driven by climate and human activities.