Manure increases temperature sensitivity of soil organic carbon by increasing soil Alphaproteobacteria, phenols, and pH and decreasing soil esters

The temperature sensitivity (Q₁₀) of soil organic carbon (SOC) is a critical parameter in SOC response models concerning climate warming, which governs both the direction and magnitude of soil carbon-climate feedback. However, the relative importance of soil organic compounds in the regulation of the Q₁₀ remains unclear, partly due to the relative stability of SOC compounds. Long-term different fertilization could change the quantity and quality of soil organic compounds. Here, a 38-year fertilization experiment combined with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) was used to identify the effect of key soil organic compounds on the Q₁₀. Five treatments were chosen: no fertilization (CK), nitrogen fertilization (N), N combined with phosphorus and potassium fertilization (NPK), manure (M), and NPK combined with manure (NPKM). The results revealed that the Q₁₀ under M and NPKM were 1.59 and 1.66, respectively, which were significantly higher than those under CK (1.35), N (1.29), and NPK (1.36). There was a positive linear relationship between the Q₁₀ and SOC (R²=0.76, P<0.01), whereby manure-enriched SOC is more vulnerable to decomposition under future warming. Among the soil organic compounds, esters and phenols predominated, representing 30.30% and 18.83% of the composition, respectively. Manure increased soil stable organic compounds relative to CK and chemical fertilizer. The increased stable organic compounds under manure led to a high Q₁₀. In addition to the positive effect of soil Alphaproteobacteria and pH on the Q₁₀, manure increased the Q₁₀ by increasing phenols and decreasing esters, whereas chemical fertilization did the opposite. These findings first provide substantial evidence that soil organic compounds play an important role in the magnitude and mechanism of SOC response to climate change. Manure-induced SOC, when compared to chemical fertilizers, conferred a heightened sensitivity to climate warming within agroecosystems.