Soil organic carbon (SOC) and soil inorganic carbon (SIC) possess an underlying dynamic interrelationship driven by abiotic and microbial factors with important effects on soil structure and carbon sequestration. However, these dynamics remain poorly understood across different aggregate scales. This study investigated the spatial distribution of SOC, SIC, microbial biomass, enzymes, and community composition within aggregates in different vegetation types, slope positions, and slope aspects in the alpine terrestrial ecosystem of the Qinghai-Tibet Plateau. Small aggregate size classes (mainly <0.053 mm) generally showed the lowest microbial activity, while dissolved organic carbon (DOC), SIC, and pH exhibited the opposite pattern. Bacterial diversity was greater than fungal diversity and less sensitive to environmental factors, while dominant phyla abundances were mostly influenced by slope position. The effect of aggregate size on community structure was unevenly distributed. The organic carbon turnover efficiency in the alpine mountains followed as alpine meadow on a sunny slope (MS) > alpine wetlands on the riverside (WR) > alpine shrubs on a shady slope (SS), and macroaggregates > microaggregates > silt + clay fraction. The pH was the major abiotic regulator of the microbially-driven organic–inorganic carbon dynamics within soil aggregates, facilitating the shift from SIC to SOC by inhibiting enzyme activity, reducing bacterial community abundance and diversity, and decreasing fungal community abundance, but increasing the fungal community diversity. This led to increased total carbon stored in soil aggregates, thereby promoting macroaggregation and stability of the soil structure.

中文翻译：

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SIC转化为SOC增强青藏高原高山生态系统的土壤固碳和土壤结构稳定性


土壤有机碳（SOC）和土壤无机碳（SIC）具有由非生物和微生物因素驱动的潜在动态相互关系，对土壤结构和碳固存具有重要影响。然而，在不同的总体规模上，这些动态仍然知之甚少。本研究调查了青藏高原高寒陆地生态系统不同植被类型、坡位和坡向的SOC、SIC、微生物量、酶和团聚体群落组成的空间分布。小聚集体尺寸类别（主要是 <0.053 毫米）通常表现出最低的微生物活性，而溶解有机碳 (DOC)、SIC 和 pH 则表现出相反的模式。细菌多样性大于真菌多样性，对环境因素不太敏感，而优势门丰度主要受坡位影响。聚集体规模对群落结构的影响分布不均匀。高山山区有机碳周转效率依次为：阳坡高山草甸（MS）>河滨高山湿地（WR）>阴坡高山灌木（SS），大团聚体>微团聚体>淤泥+粘土。 pH 值是土壤团聚体中微生物驱动的有机-无机碳动态的主要非生物调节剂，通过抑制酶活性、降低细菌群落丰度和多样性以及降低真菌群落丰度，但增加真菌群落丰度，促进从 SIC 向 SOC 的转变。社区多样性。这导致土壤团聚体中储存的总碳增加，从而促进土壤结构的宏观团聚和稳定性。