Vegetation Restoration Alters Soil Microbial Carbon Use Efficiency via Key Soil Properties and Generalist Communities in Karst Rocky Desertification

Soil microbial carbon use efficiency (CUE) is an essential metric for assessing soil carbon cycling efficiency. In contemporary biogeochemical models, microbial CUE is often treated as a constant, but it is intricately regulated by biotic and abiotic factors, especially in heterogeneous karst rocky desertification (KRD) ecosystems. In the Guizhou Huajiang KRD area, this study used ecological stoichiometry, high-throughput sequencing, analysis of variance, and partial least squares regression to evaluate CUE across three restoration types, Zanthoxylum bungeanum (ZB), Selenicereus undatus (SU), and Pennisetum × sinese (PS), with Zea mays (ZM) as control. Results showed that restoration types affected CUE. Soil bulk density (SBD), total potassium (TK), and available phosphorus (AP) were key predictors of CUE, significantly correlating with generalist communities such as Planctomycetota, Gemmatimonadota, unclassified_Gemmatimonadaceae, unclassified_Roseiflexaceae, and unclassified_Trichomeriaceae. Inconsistent variations in α- and β- diversity across types indicated CUE regulation was driven by integrated structural and functional responses. These findings highlight the importance of soil physical properties, potassium cycling, low-phosphorus adaptation, and generalist communities for species selection. Future studies must isolate vegetation and management effects, extending observations from winter to the full growing season to clarify seasonal plant-soil-microbial feedbacks.