International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 10 3.3 The influence of chemical properties of fallen leaves The chemical composition and properties of fallen leaves themselves are regarded as one of the intrinsic determinants of the decomposition rate, namely the influence of so-called "substrate quality" on decomposition (Zhang et al., 2019). There are significant differences in the carbon-nitrogen ratio, lignin content, and the content of secondary compounds such as wax and tannin among the fallen leaves of different plant species. These differences directly lead to different decomposition rates. Generally speaking, fallen leaves with high nitrogen content and low carbon-nitrogen ratio are more easily decomposed by microorganisms because they are rich in protein and soluble nutrients, which can be directly utilized by microorganisms (Zhang et al., 2020). In addition to the carbon-nitrogen ratio, secondary metabolites in leaves such as tannins, phenols, and resins can also affect the decomposition process. In summary, "delicious" fallen leaves (rich in nutrients and with many easily decomposable components) decompose quickly, while "unpalatable" fallen leaves (with low nutrients and many defensive components) decompose slowly. It is worth noting that when dead leaves of different qualities are mixed and decomposed together, a non-additive effect may occur: sometimes the mixture decomposes faster than each individual type of dead leaf, generating a "promoting" effect. This is because nutritional complementarity or microorganisms in certain leaves can utilize substances released by another leaf (Liu et al., 2022a); Sometimes, however, the mixture slows down instead, resulting in an "antagonistic" effect, which may be due to an inhibitory compound released by fallen leaves affecting the decomposition of the other party (Grossman et al., 2020). 4 Phased Dynamics During the Decomposition Process 4.1 Initial decomposition (rapid loss stage) From the moment leaves fall to their decomposition in the soil, the process does not proceed uniformly but shows distinct stages. In the initial stage of leaf decomposition, rapid mass loss often occurs, which is due to the leaching of soluble substances and the preferential degradation of easily decomposable components (Zhang et al., 2019). The initial decomposition usually lasts from several weeks to several months, with the specific length depending on environmental conditions and the quality of fallen leaves. In a warm and humid environment, this stage can be completed within 1 to 2 months. However, in a cold or dry environment, the initial stage may be prolonged because the microbial activity is limited and the leaching process is slower. However, regardless of the length, the initial stage lays the foundation for the decomposition process: a large amount of easily decomposable substances are removed, allowing the remaining fallen leaves to enter the next stage mainly characterized by structural degradation. 4.2 Mid-term decomposition (structural degradation stage) After the loss of easily decomposable substances in the early stage, the fallen leaf remains enter the mid-term decomposition stage. The main feature of this stage is the significant degradation of structural components and the relatively slowed decomposition rate process. In the mid-term stage, the main remaining organic matter includes polysaccharides such as cellulose and hemicellulose, as well as complex aromatic compounds like lignin. These components form the skeleton of plant cell walls, and their degradation requires specific enzyme systems and a relatively long time (Prescott and Vesterdal, 2021). The mid-term decomposition stage is a transitional period from rapid to slow, characterized by the degradation of a large amount of structural carbon and the beginning of nutrient release, playing a pivotal role in the material cycle of the ecosystem. 4.3 Post-decomposition (stable residual formation stage) When the remnants of fallen leaves have undergone most of the degradation in the early and middle stages, they enter the later decomposition stage. At this point, the remaining substances are mainly refractory and stable organic residues, including a high proportion of lignin and its transformation products, metabolic products left after the death of microorganisms (such as cholesterol and condensed aromatic compounds in bacterial fragments), and organic matter combined with mineral particles, etc. The further decomposition rate of this residual material is extremely slow, and it can be said to have entered the "tail decomposition" process (Prescott and Vesterdal, 2021). The late decomposition stage is the "closing" stage of the fallen leaf decomposition process, marked by the shift
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