Sphagnum wetlands are global hotspots for carbon storage, conventionally attributed to the accumulation of decay-resistant litter. However, the buildup of mineral-associated organic carbon (MAOC) with relatively slow turnover has rarely been examined therein. Here, employing both large-scale comparisons across major terrestrial ecosystems and soil survey along Sphagnum gradients in distinct wetlands, we show that Sphagnum fosters a notable accumulation of metal-bound organic carbon (OC) via activating iron and aluminum (hydr)oxides in the soil. The unique phenolic and acidic metabolites of Sphagnum further strengthen metal-organic associations, leading to the dominance of metal-bound OC in soil MAOC. Importantly, in contrast with limited MAOC sequestration potentials elsewhere, MAOC increases linearly with soil OC accrual without signs of saturation in Sphagnum wetlands. These findings collectively demonstrate that Sphagnum acts as an efficient ‘rust engineer’ that largely boosts the rusty carbon sink in wetlands, potentially increasing long-term soil carbon sequestration.

泥炭藓湿地是全球碳储存的热点，通常归因于耐腐垃圾的积累。然而，与矿物相关的有机碳（MAOC）的积累和相对缓慢的周转却很少被研究。在这里，通过对主要陆地生态系统的大规模比较和不同湿地沿泥炭藓梯度的土壤调查，我们发现泥炭藓通过激活土壤中的铁和铝（氢氧化）氧化物，促进了金属结合有机碳（OC）的显着积累。土壤。泥炭藓独特的酚类和酸性代谢物进一步加强了金属-有机结合，导致土壤 MAOC 中金属结合 OC 占主导地位。重要的是，与其他地方有限的 MAOC 封存潜力相比，MAOC 随土壤 OC 的增加呈线性增加，在泥炭藓湿地中没有饱和的迹象。这些发现共同表明，泥炭藓充当了高效的“锈蚀工程师”，在很大程度上增加了湿地中的锈碳汇，有可能增加长期土壤碳固存。