The rhizosphere is a typical soil microbial hotspot, however, not a homogeneous entity. Due to root functional differentiation, different root functional modules (i.e., absorptive roots and transport roots) can play distinct roles in microbial necromass formation and subsequent soil organic carbon (SOC) sequestration by influencing microbial metabolic activity in the surrounding soil. Yet, how microbial metabolic traits mediated by different root functional modules regulate the accumulation of microbial necromass C (MNC) in the rhizosphere remains poorly understood. Herein, we quantified and compared the differences in the contribution of MNC to SOC between the rhizosphere of two root functional modules, and explored the role of microbial metabolic traits in influencing the contribution of MNC to rhizosphere SOC in different root functional modules in two spruce ( Mast.) plantations. Our findings revealed that absorptive roots exhibited a significantly higher contribution of MNC to SOC (32.9–37.5%) compared to transport roots (27.7–30.5%) in the rhizosphere. This suggests that absorptive roots possess a greater ability to promote MNC accumulation in the rhizosphere than transport roots. This observation was mainly attributed to the difference in the trade-offs between microbial growth and investment traits between the two root functional modules. Specifically, the rhizosphere of absorptive roots had greater microbial C use efficiency (CUE), faster growth and turnover rates, lower respiratory quotients and biomass-specific enzyme activity than did those of transport roots, suggesting that absorptive roots support greater microbial growth yields and subsequently greater necromass production. Collectively, our findings demonstrate that the contribution of MNC to SOC in the rhizosphere largely depends on the trade-offs of microbial metabolic traits mediated by root functional differentiation. Our study also provides novel and direct empirical evidence supporting the need to integrate function-based fine root classifications with the different contributions of MNC to SOC sequestration in the rhizosphere into land surface models of C cycling.

中文翻译：

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微生物代谢特征驱动吸收根和运输根根际微生物坏死物对土壤有机碳的差异贡献


根际是典型的土壤微生物热点，但不是一个均质实体。由于根系功能分化，不同的根系功能模块（即吸收根和运输根）可以通过影响周围土壤中的微生物代谢活动，在微生物坏死物形成和随后的土壤有机碳（SOC）固存中发挥不同的作用。然而，不同根功能模块介导的微生物代谢特征如何调节根际微生物坏死物C（MNC）的积累仍知之甚少。在此，我们量化并比较了两种云杉根际功能模块中MNC对SOC贡献的差异，并探讨了微生物代谢性状对两种云杉不同根功能模块中MNC对根际SOC贡献的影响作用。桅杆。）种植园。我们的研究结果表明，与根际运输根（27.7-30.5%）相比，吸收根对 SOC 的贡献显着更高（32.9-37.5%）。这表明吸收根比运输根具有更大的促进根际 MNC 积累的能力。这一观察结果主要归因于两个根功能模块之间微生物生长和投资性状之间的权衡差异。具体而言，与运输根相比，吸收根的根际具有更高的微生物碳利用效率（CUE）、更快的生长和周转率、更低的呼吸商和生物量特异性酶活性，这表明吸收根支持更高的微生物生长产量，随后更大的死灵体产量。 总的来说，我们的研究结果表明，MNC 对根际 SOC 的贡献很大程度上取决于根功能分化介导的微生物代谢特征的权衡。我们的研究还提供了新颖且直接的经验证据，支持需要将基于功能的细根分类与 MNC 对根际 SOC 封存的不同贡献整合到碳循环的地表模型中。