It remains unclear whether microbial carbon limitation exists in the rhizosphere, a microbial hotspot characterized by intensive labile carbon input. Here, we collected rhizosphere soils attached to absorptive and transport roots and bulk soils in three alpine coniferous forests and evaluated the limiting resources of microbes based on the responses of microbial growth (¹⁸O incorporation into DNA) and respiration to full-factorial amendments of carbon, nitrogen, and phosphorus. The results showed that adding carbon enhanced microbial growth and respiration rates in the rhizosphere soils by 1.2- and 10.3-fold, respectively, indicating the existence of carbon limitation for both anabolic and catabolic processes. In contrast, the promoting effects of nutrient addition were weak or manifested only after the alleviation of carbon limitation, suggesting that nutrients were co-limiting or secondarily limiting resources. Moreover, the category and extent of microbial resource limitations were comparable between the rhizosphere of absorptive and transport roots, and between the rhizosphere and bulk soils. Overall, our findings offer direct evidence for the presence of microbial carbon limitation in the rhizosphere.

目前尚不清楚根际是否存在微生物碳限制，根际是一个以大量不稳定碳输入为特征的微生物热点。在这里，我们收集了三个高山针叶林中附着于吸收和运输根的根际土壤和大块土壤，并根据微生物生长（ ¹⁸ O 掺入 DNA）和呼吸对碳全因子修正的响应评估了微生物的限制资源。 、氮和磷。结果表明，添加碳可使根际土壤中的微生物生长和呼吸速率分别提高 1.2 倍和 10.3 倍，表明合成代谢和分解代谢过程都存在碳限制。相比之下，养分添加的促进作用较弱或仅在碳限制缓解后才显现，表明养分对资源具有共同限制或次要限制作用。此外，吸收根和运输根的根际以及根际和大块土壤之间微生物资源限制的类别和程度具有可比性。总的来说，我们的研究结果为根际微生物碳限制的存在提供了直接证据。