Rhizosheaths are aggregated, sheath-like soils that physically adhere to root surface, and they form on herbaceous plant roots worldwide, especially in semiarid grasslands. Representing a strong root−soil−microbe interaction, the rhizosheaths are expected to have distinct soil organic carbon (SOC) signatures from rhizosphere soils of non-rhizosheath forming plants. However, such signatures remain unclear, which hinders our understanding of root effects on SOC cycling in grasslands. We compared SOC characteristics between rhizosheath and non-rhizosheath soils of eight herbaceous plant species, collected from a semiarid grassland of North China, using solid-state ¹³C nuclear magnetic resonance spectroscopy and biomarker analyses. We further examined the temporal dynamics of SOC characteristics of rhizosheath soils from early, middle, and late plant growth stages. Compared to non-rhizosheath SOC, rhizosheath SOC had more root inputs of both labile substrates (carbohydrates and free alkanoic acids) and relatively recalcitrant suberin- and lignin-derived compounds. Moreover, the labile inputs provided more substrates for microbial degradation of cutin-derived compounds. These indicators of labile substrate availability increased significantly from the early to late growth stages. Overall, our findings clarify the molecular characteristics of rhizosheath SOC and its temporal dynamics, both of which suggest a critical role of rhizosheath in shaping the rhizosphere microenvironment and regulating SOC cycling.

根鞘是聚集的鞘状土壤，物理粘附在根表面，它们在世界各地的草本植物根上形成，特别是在半干旱草原中。根鞘代表了强烈的根-土壤-微生物相互作用，预计根鞘与非根鞘形成植物的根际土壤具有不同的土壤有机碳 (SOC) 特征。然而，这些特征仍不清楚，这阻碍了我们对草地 SOC 循环的根系效应的理解。^{我们使用固态13}比较了从华北半干旱草地采集的八种草本植物的根鞘和非根鞘土壤的 SOC 特征。C核磁共振波谱和生物标志物分析。我们进一步研究了植物生长早期、中期和晚期根鞘土壤 SOC 特征的时间动态。与非根鞘 SOC 相比，根鞘 SOC 具有更多的不稳定底物（碳水化合物和游离链烷酸）和相对顽固的木栓质和木质素衍生化合物的根输入。此外，不稳定的输入为角质衍生化合物的微生物降解提供了更多的底物。从早期到晚期生长阶段，这些不稳定底物可用性的指标显着增加。总体而言，我们的研究结果阐明了根鞘 SOC 的分子特征及其时间动态，这两者都表明根鞘在塑造根际微环境和调节 SOC 循环方面发挥着关键作用。