Filimonenko Ekaterina, Kuzyakov Yakov
National Key Laboratory of Wheat Improvement, College of Agronomy, Shandong Agricultural University, Tai'an, Shandong, China.
Sirius University of Science and Technology, Sirius Federal Area, Sochi, Russia.
Glob Chang Biol. 2025 Sep;31(9):e70472. doi: 10.1111/gcb.70472.
The activation energy (E) is the minimum energy necessary for (bio)chemical reactions acting as an energy barrier and defining reaction rates, for example, organic matter transformations in soil. Based on the E database of (i) oxidative and hydrolytic enzyme activities, (ii) organic matter mineralization and CO production, (iii) heat release during soil incubation, as well as (iv) thermal oxidation of soil organic matter (SOM), we assess the E of SOM transformation processes. After a short description of the four approaches to assess these E values-all based on the Arrhenius equation-we present the E of chemical oxidation (79 kJ mol, based on thermal oxidation), microbial mineralization (67 kJ mol, CO production), microbial decomposition (40 kJ mol, heat release), and enzyme-catalyzed hydrolysis of polymers and cleavage of mineral ions of nutrients (33 kJ mol, enzyme driven reactions) from SOM. The catalyzing effects of hydrolytic and oxidative enzymes reduce E of SOM decomposition by more than twice that of its chemical oxidation. The E of enzymatic cleavage of mineral ions of N, P, and S from their organic compounds is 9 kJ mol lower (corresponding to 40-fold faster reactions) than the hydrolysis of N-, P-, and S-free organic polymers. In soil, where organic compounds are physically protected and enzymes are partly deactivated, microbial mineralization is ~140-fold faster compared to its pure chemical oxidation. Because processes with higher E are more sensitive to temperature increase, global warming will accelerate the decomposition of stable organic compounds and boost the C cycle much stronger than the cycling of nutrients: N, P, and S. Consequently, the stoichiometry of microbially utilized compounds in warmer conditions will shift toward organic pools with higher C/N ratios. This will decouple the cycling of C and nutrients: N, P, and S. Overall, the E of (bio)chemical transformations of organic matter in soil enables to assess process rates and the inherent stability of SOM pools, as well as their responses to global warming.
活化能（E）是（生物）化学反应发生所需的最低能量，它充当能量屏障并决定反应速率，例如土壤中有机物的转化。基于以下方面的E数据库：（i）氧化酶和水解酶活性，（ii）有机物矿化和CO产生，（iii）土壤培养期间的热释放，以及（iv）土壤有机质（SOM）的热氧化，我们评估了SOM转化过程的E。在简要描述了评估这些E值的四种方法（均基于阿伦尼乌斯方程）之后，我们给出了化学氧化（基于热氧化为79 kJ/mol）、微生物矿化（67 kJ/mol，CO产生）、微生物分解（40 kJ/mol，热释放）以及聚合物的酶促水解和养分矿质离子的裂解（33 kJ/mol，酶驱动反应）的E值，这些均来自SOM。水解酶和氧化酶的催化作用使SOM分解的E降低至其化学氧化的E的两倍以上。从有机化合物中酶促裂解N、P和S的矿质离子的E比不含N-、P-和S的有机聚合物的水解低9 kJ/mol（相应反应速度快40倍）。在土壤中，有机化合物受到物理保护且酶部分失活，微生物矿化比其纯化学氧化快约140倍。由于具有较高E的过程对温度升高更敏感，全球变暖将加速稳定有机化合物的分解，并比养分（N、P和S）循环更有力地促进碳循环。因此，在温暖条件下微生物利用的化合物的化学计量将转向具有更高C/N比的有机库。这将使碳与养分（N、P和S）的循环脱钩。总体而言，土壤中有机物（生物）化学转化的E能够评估过程速率、SOM库的固有稳定性及其对全球变暖的响应。
