Beyond Diversity: Does Microbial Composition Drive Soil Multifunctionality in Cultivated Wetlands?

ABSTRACT Wetlands are major global carbon sinks, yet their extensive conversion to cropland profoundly alters soil carbon and nutrient dynamics, creating uncertainty about soil multifunctionality. This uncertainty is particularly acute in intensively managed systems, where links between microbial communities and multifunctionality remain poorly understood. Here, we sampled four paired natural and adjacent paddy-cultivated wetlands in Northeast China to investigate how prokaryotic and eukaryotic communities are associated with soil multifunctionality. Cultivation significantly reduced soil multifunctionality in both surface and subsurface soils. Although the eukaryotic Shannon diversity declined significantly in surface soils, neither prokaryotic nor eukaryotic alpha diversity was associated with soil multifunctionality. In contrast, principal coordinate analysis revealed marked compositional shifts in both prokaryotic and eukaryotic communities following cultivation, evident in both surface and subsoil layers. Furthermore, random forest models and structural equation models indicated that prokaryotic composition at both phylum and species levels was more strongly associated with variations in surface-soil multifunctionality, whereas eukaryotic composition at the species level was more strongly associated with subsoil multifunctionality. Collectively, these findings indicate that cultivation-induced shifts in microbial community composition are more strongly associated with changes in soil multifunctionality than are alterations in microbial diversity.