EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-2229 Long-term throughfall exclusion reduced soil organic carbon towards higher soil microbial carbon use efficiency and lower microbial enzyme activities in <em>Phyllostachys edulis</em> plantations Mao Yilian 1 2 5 Xue Xupeng 1 2 5 Ge Xiaogai 1 2 Ge Tida 3 Yao Hongwen 4 Zhou Benzhi 1 2 Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou, Zhejiang, 311400, China Qianjiangyuan Forest Ecosystem Research Station, National Forestry and Grassland Administration, Hangzhou 311400, Zhejiang, China State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection of Ministry of Agriculture and Zhejiang Province, Institute of Plant Virology, Ningbo University, Ningbo 315211, China Forest Resource Monitoring Center of Zhejiang, Province, Hangzhou 310020, Zhejiang, China These authors contributed equally to this work. 21 05 2026 2026 1 37 Copyright: © 2026 Yilian Mao et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2229/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2229/egusphere-2026-2229.pdf

Soil microbial carbon utilization efficiency (CUE) serves as a crucial metric for evaluating the effectiveness with which microbes assimilate organic carbon, acting as a vital benchmark for assessing the potential of soil carbon sequestration. Previous studies have shown that drought can significantly affect microbial CUE, which is crucial for the carbon cycle in forest ecosystems. However, the mechanisms of microbial CUE on soil carbon stability under drought conditions are not well understood. In this study, a throughfall exclusion experiment was conducted in subtropical <em>Phyllostachys edulis</em> plantations (The control, CK; throughfall exclusion, T). The results showed that drought increased microbial CUE by 9.12% (<em>p</em>&lt;0.05) and 2.56% in 0&ndash;10 cm and 10&ndash;20 cm soil layers, respectively. Soil organic carbon (SOC), soil particulate organic carbon (POC), soluble organic carbon (DOC), and easily oxidized organic carbon (EOC) all significantly decreased, while the proportion of mineral-associated organic carbon (MAOC) in SOC increased by 4.1% and 6.3% (<em>p</em>&lt;0.05) at two layers, respectively. Microbial CUE was positively correlated with POC/SOC ratio and MAOC/SOC ratio, indicating that variation of SOC components substrate quality was an important factor driving microbial physiological changes. Structural equation model (SEM) further showed that soil polyphenol oxidase (PPO) and cellobiohydrolase (CBH) enzymes were the main factors driving changes in microbial CUE. Our results suggested that drought indirectly regulates the storage and transformation of SOC by affecting microbial community structure and function, which would have a profound impact on the carbon cycle of forest ecosystems.