Integrated organic amendments prevent the rise in temperature sensitivity of soil organic carbon decomposition in micro-aggregates via mineral and chemical stabilization

The temperature sensitivity of soil organic carbon (SOC) decomposition (Q 10 ) is critical for predicting terrestrial carbon (C)-climate feedbacks under global warming. Yet, the variations of Q 10 regulated by mineral mediation and chemical stability across large (LA, >2 mm), small (SA, 0.25–2 mm), and micro-aggregates (MA, <0.25 mm), particularly in response to fertilization practices, remain unclear. Based on a 37-year field trial, we evaluated Q 10 differences among aggregates and their links to mineral phases, chemical stability, and microbial properties under chemical (nitrogen alone, N; and N, phosphorus, and potassium combination, NPK) and organic (manure alone, M; and M combined with NPK, NPKM) fertilization. Compared to no fertilization, organic fertilization increased Q 10 in SA (by 127.9% under M and 91.6% under NPKM) and in MA under M (by 27.6%), but not in LA. Chemical fertilization showed minimal influence on Q 10 across aggregates, except for N, which increased Q 10 in SA by 96.9%. Amorphous iron and aluminum oxides increased most under organic amendments, especially NPKM (70.7–147.9%). Under organic fertilization, M increased the chemical stabilization of LA by 91.6% but reduced it in MA, while NPKM enhanced the chemical stabilization in MA by 126.5% without affecting LA. Structural equation modeling revealed that during the shift from chemical to organic fertilization, the positive responses of amorphous iron and aluminum oxides and key bacteria (e.g., Blastocatellia) were related to the unchanged Q 10 of LA, whereas those of free iron and aluminum oxides and chemical stability (aromatic and amide compounds) were linked to the limited increase in MA Q 10 . Conversely, the increased proportion of SA was associated with the increase in its Q 10 . These findings revealed the contrasting effects of organic amendments (especially for M): Q 10 remained unchanged in LA but increased in SA, driven by differences in mineral attributes, organic compound stability, and aggregate composition. Therefore, integrating organic amendments with chemical fertilizers is recommended as a sustainable soil management strategy to stabilize aggregate-associated SOC and mitigate positive climate feedbacks.