Heteropolymer humic substances (HS) are the largest constituents of soil organic matter and are key components that affect plant and microbial growth in maritime Antarctic tundra. We investigated HS decomposition in Antarctic tundra soils from distinct sites by incubating samples at 5°C or 8°C (within a natural soil thawing temperature range of −3.8°C to 9.6°C) for 90 days (average Antarctic summer period). This continuous 3-month artificial incubation maintained a higher total soil temperature than that in natural conditions. The long-term warming effects rapidly decreased HS content during the initial incubation, with no significant difference between 5°C and 8°C. In the presence of Antarctic tundra soil heterogeneity, the relative abundance of Proteobacteria (one of the major bacterial phyla in cold soil environments) increased during HS decomposition, which was more significant at 8°C than at 5°C. Contrasting this, the relative abundance of Actinobacteria (another major group) did not exhibit any significant variation. This microcosm study indicates that higher temperatures or prolonged thawing periods affect the relative abundance of cold-adapted bacterial communities, thereby promoting the rate of microbial HS decomposition. The resulting increase in HS-derived small metabolites will possibly accelerate warming-induced changes in the Antarctic tundra ecosystem.

中文翻译：

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低温适应菌降解南极土壤腐殖质的温度敏感性

杂聚腐殖质（HS）是土壤有机质的最大成分，是影响南极海洋苔原植物和微生物生长的关键成分。我们通过在 5°C 或 8°C（在-3.8°C 至 9.6°C 的自然土壤解冻温度范围内）培养样品 90 天（平均南极夏季），研究了来自不同地点的南极苔原土壤中的 HS 分解。这种连续 3 个月的人工孵化保持了比自然条件下更高的土壤总温度。长期升温效应在初始孵化期间迅速降低了 HS 含量，5°C 和 8°C 之间没有显着差异。在存在南极苔原土壤异质性的情况下，变形菌的相对丰度（寒冷土壤环境中的主要细菌门之一）在 HS 分解过程中增加，这在 8°C 比在 5°C 时更显着。与此相反，放线菌（另一个主要群体）的相对丰度没有表现出任何显着变化。这项微观研究表明，较高的温度或较长的解冻期会影响适应冷的细菌群落的相对丰度，从而促进微生物 HS 分解的速率。由此产生的 HS 衍生的小代谢物的增加可能会加速南极苔原生态系统因变暖引起的变化。