Soil organic carbon (SOC) is the largest terrestrial carbon (C) pool and is vulnerable to climate and land-use changes. Promoting the stabilization of SOC will reduce climate change-induced C losses. Mineral-associated organic carbon (MAOC), formed by the association of organic carbon with silt- and clay-sized minerals, is the major stabilized SOC fraction and key to sustaining soil health and mitigating climate change. However, the role of silt and clay in MAOC formation remains unclear in dryland ecosystems where microbes and plants are frequently under water stress. The current paradigm assumes that the main role of silt and clay is to adsorb and aggregate organic compounds. In a semi-arid environment, using a naturally occurring gradient of increasing soil silt and clay content partially due to aeolian dust inputs, we show that silt and clay also enhanced microbial decomposition of plant C inputs and microbial turnover, increasing microbial C inclusion into the MAOC pool. Finer-textured soils had higher soil water availability and higher volume of habitat available to microorganisms. The enhanced microbial processing interacted with changes in plant C inputs to further control the relative contribution of MAOC to SOC. Our results suggest SOC models should include soil textural effects on microbial activities and microbial C production in addition to physical protection of SOC. Our study also suggests that aeolian dust inputs can increase soil silt and clay contents and improve nutrient availability in dryland ecosystems, potentially mitigating the SOC loss under climate change and increasing the resilience of ecosystems to drought.

中文翻译：

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淤泥和粘土在稳定土壤有机碳形成和积累中的双重作用

土壤有机碳（SOC）是最大的陆地碳（C）库，容易受到气候和土地利用变化的影响。促进SOC的稳定将减少气候变化引起的碳损失。矿物伴生有机碳 (MAOC) 由有机碳与淤泥和粘土大小的矿物结合形成，是主要的稳定 SOC 部分，也是维持土壤健康和缓解气候变化的关键。然而，在微生物和植物经常受到水分胁迫的旱地生态系统中，淤泥和粘土在 MAOC 形成中的作用仍不清楚。目前的范式假设淤泥和粘土的主要作用是吸附和聚集有机化合物。在半干旱环境中，利用部分由于风尘输入而导致的土壤淤泥和粘土含量增加的自然梯度，我们发现淤泥和粘土还增强了植物碳输入的微生物分解和微生物周转，增加了微生物碳的含量MAOC 池。质地更细的土壤具有更高的土壤水分可用性和更多的微生物可用栖息地。增强的微生物处理与植物 C 输入的变化相互作用，进一步控制 MAOC 对 SOC 的相对贡献。我们的结果表明，除了 SOC 的物理保护之外，SOC 模型还应包括土壤质地对微生物活动和微生物碳生产的影响。我们的研究还表明，风尘输入可以增加土壤淤泥和粘土含量，提高旱地生态系统的养分利用率，有可能减轻气候变化下的有机碳损失，提高生态系统对干旱的恢复能力。