Department of Applied Physics, University of Santiago de Compostela, Campus Terra, 27002, Lugo, Spain.
Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Belgrade, Serbia.
Sci Rep. 2024 Jul 18;14(1):16644. doi: 10.1038/s41598-024-67590-w.
Thermodynamics is a vast area of knowledge with a debatable role in explaining the evolution of ecosystems. In the case of soil ecosystems, this role is still unclear due to difficulties in determining the thermodynamic functions that are involved in the survival and evolution of soils as living systems. The existing knowledge is largely based on theoretical approaches and has never been applied to soils using thermodynamic functions that have been experimentally determined. In this study, we present a method for the complete experimental thermodynamic characterization of soil organic matter. This method quantifies all the thermodynamic functions for combustion and formation reactions which are involved in the thermodynamic principles governing the evolution of the universe. We applied them to track the progress of soil organic matter with soil depth in mature beech forests. Our results show that soil organic matter evolves to a higher degree of reduction as it is mineralized, yielding products with lower carbon but higher energy content than the original organic matter used as reference. These products have higher entropy than the original one, demonstrating how the soil ecosystem evolves with depth, in accordance with the second law of thermodynamics. The results were sensitive to soil organic matter transformation in forests under different management, indicating potential applicability in elucidating the energy strategies for evolution and survival of soil systems as well as in settling their evolutionary states.
热力学是一个知识领域，它在解释生态系统的演化方面具有一定的争议性。在土壤生态系统中，由于难以确定与土壤作为生命系统的生存和演化相关的热力学函数，其作用仍然不明确。现有知识主要基于理论方法，从未应用于使用实验确定的热力学函数来研究土壤。在本研究中，我们提出了一种全面实验热力学表征土壤有机质的方法。该方法量化了所有与燃烧和形成反应相关的热力学函数，这些反应涉及到控制宇宙演化的热力学原理。我们将其应用于追踪成熟山毛榉林中土壤有机质随深度的变化。我们的结果表明，随着土壤有机质的矿化，它会向更高的还原程度演化，产生的产物碳含量较低，但能量含量比原始有机质作为参考时更高。这些产物的熵值比原始产物高，表明土壤生态系统如何根据热力学第二定律随深度演化。结果对不同管理下森林中土壤有机质的转化很敏感，表明其在阐明土壤系统进化和生存的能量策略以及确定其进化状态方面具有潜在的适用性。
