International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 07 This study will discuss a series of functional contributions of leaf decomposition to the ecosystem, summarize the main biological and abiotic factors driving leaf decomposition, elaborate on the phased dynamic laws of the decomposition process, as well as the role of leaf decomposition in the cycling of elements such as carbon, nitrogen, and phosphorus. At the same time, it will also combine the case differences in different regions and the research progress under the global change scenario. Look forward to the future research directions. The decomposition of fallen leaves has irreplaceable ecological significance in maintaining soil fertility, promoting ecosystem stability and responding to global changes. 2 The Ecological Significance of Leaf Decomposition 2.1 Support for vegetation regeneration and primary productivity Leaf decomposition replenishes soil fertility by releasing nutrients, thereby directly supporting the regeneration of vegetation and the primary productivity of ecosystems (Njoroge et al., 2022). When the dead branches and fallen leaves of plants are returned to the soil, the decomposition mediated by microorganisms and soil animals converts the essential nutrients such as nitrogen, phosphorus and potassium contained therein into inorganic forms for re-absorption and utilization by the plant roots. This nutrient cycle ensures the continuous growth of vegetation and the renewal of the community (Guo et al., 2021). Studies have shown that the higher the decomposition rate and nutrient release rate of an ecosystem, the stronger its soil nutrient supply capacity, and thus can maintain higher plant productivity (Liu et al., 2022b). For instance, in highly productive forest ecosystems, the rapid decomposition of fallen leaves provides a large amount of mineral nutrients to the soil each year, supporting the metabolism and growth of trees (Zhang et al., 2021). In addition, in some cases, plants can also influence the growth of themselves and their neighboring plants by adjusting the nutrient content and decomposition rate of their fallen leaves. This is known as the "nutrient feedback" effect: fallen leaves with high nutrient content and easy decomposition help form fertile soil, thereby promoting the growth of seedlings or communities of this plant species. However, hard-to-decompose fallen leaves may cause soil nutrient deficiency, inhibit other species, and thereby indirectly maintain the dominant position of this plant (Tennakoon, 2021). 2.2 Improvement of soil structure and physical and chemical properties The humus and organic residues formed during the decomposition of fallen leaves are the main sources of soil organic matter and can significantly improve the structure and physicochemical properties of the soil (Figure 1) (Prescott and Vesterdal, 2021). Under the action of decomposers, some carbon substances in fallen leaves are transformed into stable soil organic carbon components, increasing the content of soil organic matter. This plays an important role in the formation of aggregates and the stability of soil structure. High organic matter content enables soil particles to bond into aggregates through binders such as microbial polysaccharides, forming a good aggregate structure and enhancing soil porosity and looseness (Liu et al., 2023). This not only improves the soil aeration condition, but also enhances the soil's water-holding capacity, which helps maintain soil moisture and buffer water stress during drought (Krishna and Mohan, 2017). Meanwhile, humus itself has a strong cation exchange capacity, which can adsorb and slowly release nutrient ions, playing the role of a nutrient buffer reservoir, improving nutrient utilization efficiency and maintaining soil fertility (Prescott and Vesterdal, 2021). Research has found that in natural forest soils with long-term low application of inorganic fertilizers, a large amount of soil nutrients (such as nitrogen and phosphorus) are stored in humus formed by the decomposition of fallen leaves. The accumulation of humus enables the soil to have the ability to continuously supply nutrients, which is conducive to the stable growth of vegetation (Loranger et al., 2002). In addition, the organic acids and other substances released during the decomposition of fallen leaves can also buffer the pH value of the soil, complex harmful metal ions in the soil, and optimize the chemical environment of the soil.
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