International Journal of Molecular Ecology and Conservation, 2025, Vol.15 http://ecoevopublisher.com/index.php/ijmec © 2025 EcoEvoPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved.
International Journal of Molecular Ecology and Conservation, 2025, Vol.15 http://ecoevopublisher.com/index.php/ijmec © 2025 EcoEvoPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. EcoEvoPublisher is an international Open Access publishing platform that publishes scientific journals in the field of ecology and evolution registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada. Publisher EcoEvo Publisher Edited by Editorial Team of International Journal of Molecular Ecology and Conservation Email: edit@ijmec.ecoevopublisher.com Website: http://ecoevopublisher.com/index.php/ijmec Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada International Journal of Molecular Ecology and Conservation (ISSN 1927-663X) is an open access, peer reviewed journal published online by EcoEvoPublisher. The journal is considering all the latest and outstanding research articles, letters and reviews in all aspects of molecular ecology and conservation, containing the contents of the ranges from the applied to the theoretical in molecular ecology and nature conservation, the policy and management with comprehensive and applicable information; the ecological bases for the conservation of ecosystems, species, genetic diversity, the restoration of ecosystems and habitats; as well as the expands the field of ecology and conservation work. All the articles published in International Journal of Molecular Ecology and Conservation are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. EcoEvoPublisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors’ copyrights.
International Journal of Molecular Ecology and Conservation (online), 2025, Vol. 15, No.5 ISSN 1927-663X https://ecoevopublisher.com/index.php/ijmec © 2025 EcoEvoPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Latest Content Decomposition Processes and Nutrient Cycling in Leaf Litter Ecosystems Jiong Fu International Journal of Molecular Ecology and Conservation, 2025, Vol. 15, No. 5, 206-216 Ecosystem Engineering by Beavers: Impacts on Biodiversity and Hydrology Manman Li International Journal of Molecular Ecology and Conservation, 2025, Vol. 15, No. 5, 217-228 Commensal Relationships in Forests: The Ecological Role of Epiphytes Xianliang Xu International Journal of Molecular Ecology and Conservation, 2025, Vol. 15, No. 5, 229-239 Survival and Suppression: Black Walnut’s Allelopathic Strategies Chuchu Liu, Zhonggang Li International Journal of Molecular Ecology and Conservation, 2025, Vol. 15, No. 5, 240-248 Spatial Behavior and Population Ecology: The Role of Territoriality Xuming Lyu, Yeping Han International Journal of Molecular Ecology and Conservation, 2025, Vol. 15, No. 5, 249-259
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 06 Review Open Access Decomposition Processes and Nutrient Cycling in Leaf Litter Ecosystems Jiong Fu Hainan Provincial Key Laboratory for Crop Molecular Breeding, Sanya, 572025, Hainan, China Corresponding email: jiong.fu@hitar.org International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5 doi: 10.5376/ijmec.2025.15.0021 Received: 16 Jul., 2025 Accepted: 25 Aug., 2025 Published: 08 Sep., 2025 Copyright © 2025 Fu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Fu J., 2025, Decomposition processes and nutrient cycling in leaf litter ecosystems, International Journal of Molecular Ecology and Conservation, 15(5): 206-216 (doi: 10.5376/ijmec.2025.15.0021) Abstract This study reviews the ecological significance, driving mechanisms, phased dynamics and role in nutrient cycling of the deciduous decomposition process, and focuses on evaluating the responses of decomposition and nutrient cycling in the context of global change. Research has found that the decomposition of fallen leaves supports vegetation regeneration and primary productivity by releasing nutrients, enhances soil fertility and structural stability, and strengthens the ecosystem's resistance to disturbances. The decomposition process is driven by a variety of biological and abiotic factors: the diversity and functional division of decomposers (microorganisms and soil invertebrates), environmental conditions such as temperature and humidity in the habitat, and the chemical quality of fallen leaves themselves jointly determine the decomposition rate. Meanwhile, the decomposition of fallen leaves has a distinct phased dynamic pattern. The rapid loss of soluble substances in the early stage, the degradation of structural substances in the middle stage, and the formation of stable residues (humus) in the later stage occur in stages. This study emphasizes that the decomposition of fallen leaves is an important process for maintaining ecosystem functions, with the aim of better predicting and managing the nutrient cycling of ecosystems under climate change and human interference. Keywords Decomposition of fallen leaves; Nutrient cycling; Diversity of decomposers; Decomposition rate; Global changes 1 Introduction Fallen leaves (the layer of dead branches and leaves), as one of the main forms for the return of organic matter and nutrients to the soil in terrestrial ecosystems, play a key role in maintaining the material cycle and energy flow of the ecosystem (Chen et al., 2021). Vegetation introduces a large amount of carbon and nutrients into the soil through fallen leaves every year. It is estimated that a considerable portion (over 50%) of the fixed primary productivity of forests eventually returns to the soil in the form of fallen leaves, thus becoming an important source of soil fertility and the dominant pathway for nutrient cycling (Liu et al., 2022a; Yuan et al., 2024). The decomposition process of fallen leaves is the basis of soil formation and nutrient redistribution. Its rate and products directly affect the accumulation of soil organic matter, nutrient availability, and the carbon sink/source function of the ecosystem (Friedlingstein et al., 2020). Meanwhile, the energy and nutrients released by the decomposition of fallen leaves provide food sources for soil biological communities, maintaining the normal operation of the soil food web and microbial functions. This process not only supports the continuous growth of vegetation and the primary productivity of the ecosystem, but also shapes the stability and anti-interference ability of the ecosystem by influencing soil structure, fertility and moisture conditions (Prescott and Vesterdal, 2021). However, the process of leaf decomposition is influenced by multiple factors: including the diversity and functional roles of decomposers such as microorganisms and soil invertebrates, environmental conditions such as temperature and moisture, as well as the chemical composition of the leaves themselves (Schwieger et al., 2025). In recent years, with the intensification of processes such as global climate change, increased nitrogen deposition, loss of biodiversity and invasion of alien species, significant changes may occur in the deciduous decomposition and nutrient cycling processes (Hu et al., 2022; Wu et al., 2025). In view of this, it is necessary to systematically sort out the ecological significance and mechanism of leaf decomposition, and evaluate the response mechanism of the decomposition process and nutrient cycling under the background of global change.
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.
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 08 Figure 1 The continuum of litter decomposition pathways (Adopted from Prescott and Vesterdal, 2021) Image caption: Showing influence of soil and parent material characteristics on soil biota, litter quality, decomposition pathway, and SOM and humus forms. In natural forests, the dominant tree species reflect these site conditions. Planted trees can shift conditions to some extent (Adopted from Prescott and Vesterdal, 2021) 2.3 Contribution to the stability and anti-interference capacity of the ecosystem The stability and anti-interference ability of an ecosystem largely depend on whether its nutrient cycling is balanced and continuous, and leaf decomposition plays an indispensable regulatory role in it (da Silva et al., 2018). Stable and efficient leaf decomposition means that the nutrients within the ecosystem can be recycled and reused, reducing the reliance on external inputs, thereby enabling the ecosystem to have a stronger self-regulation ability in the face of external environmental fluctuations (such as abnormal climate, changes in nutrient deposition, etc.) (Elias et al., 2020).
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 09 Research also shows that communities of decomposers with higher diversity help ecosystems maintain functional stability under environmental stress. This is known as "functional redundancy" and the "insurance effect" - different decomposers respond differently to environmental changes. When the functions of certain species decline due to disturbances, other species can take over their functions. This ensures that the decomposition process and nutrient supply are not interrupted (Njoroge et al., 2022). The continuous process of leaf decomposition can also form a thin layer rich in humus on the soil surface, which helps to reduce the direct erosion of the soil by heavy rain, lower soil erosion, and protect the ecosystem from soil degradation caused by disturbance. This is particularly important for maintaining the long-term stability of the ecosystem. In addition, biological disturbances such as the invasion of alien plants are also closely related to the process of leaf decomposition. Invasive plants often change soil nutrient conditions and microbial communities through their fallen leaves to facilitate their own growth (Bruelheide et al., 2018). 3 The Key Driving Mechanism of Leaf Decomposition 3.1 Biological factors: diversity and functional division of decomposers The decomposer community is the direct executor of the leaf decomposition process, and its composition and function significantly affect the decomposition rate and pathways. Decomposers mainly include two levels: microorganisms (bacteria, fungi, etc.) and soil invertebrates (such as worms, arthropods, etc.). Microorganisms, especially fungi, are the main force in the degradation of complex organic matter such as lignin and cellulose (Purahong et al., 2016). Bacteria play a synergistic role in the decomposition process, especially in the later stage of decomposition. When the substrate becomes relatively simple, bacteria multiply in large numbers and participate in the mineralization of remaining organic substances (such as soluble sugars and amino acids), converting them into inorganic nutrients (Wang et al., 2021). In addition to microorganisms, soil animals (also known as disintegrators) further accelerate the decomposition process through mechanical crushing and ingestion. Another key aspect of biological factors is the diversity of decomposers: an increase in diversity often leads to functional complementarity and redundancy, thereby enhancing the overall decomposition efficiency. Different types of decomposers are adept at breaking down organic matter of various components or playing different roles in the decomposition chain. For instance, some fungi are good at initially invading and decomposing easily decomposable components, while others can degrade lignin that is resistant to decomposition, etc. Among soil animals, some feed on dead leaf fragments, while others prey on microbial communities, influencing microbial activity through trophic level relationships. This functional division of labor and collaboration make the decomposition process more comprehensive and efficient (Liu et al., 2020). 3.2 Abiotic factors: physical and chemical regulation of environmental conditions Environmental conditions are external driving factors that affect the rate and path of leaf decomposition, among which temperature and moisture are the two most important variables (Wu et al., 2025). Temperature directly affects the decomposition process by regulating the metabolic rate of decomposing microorganisms: generally speaking, within a certain range, for every 10℃ increase in temperature, the decomposition rate approximately doubles (i.e., the Q10 effect), because the enzymatic reactions and reproduction rates of microorganisms significantly accelerate at higher temperatures (Zhao et al., 2020). Adequate moisture (moist soil and litter) can promote the growth of microorganisms and increase the rate of enzyme diffusion. The activities of soil animals also become more frequent, thereby accelerating the decomposition process. Conversely, overly dry conditions can cause microorganisms to stagnate and enter dormancy, reduce the activities of soil animals, and limit decomposition (Xi et al., 2024). In addition to temperature and humidity, the physical and chemical properties of the soil among abiotic factors also play a role. For instance, soil pH can affect the composition of microbial communities and the activity of enzymes: a neutral and slightly acidic environment is usually most favorable for most decomposers, including bacteria and fungi, while overly acidic or overly alkaline conditions can reduce decomposition efficiency (Tie et al., 2023).
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
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 11 from rapid to extremely slow decomposition and the transformation from degradable substances to humus. Through this stage, the ecosystem transforms the short-term turnover of fallen soil into a long-term accumulation of soil organic matter, achieving a partial "retention" of carbon and nutrients. 5 Decomposition of Fallen Leaves and Circulation of Nutrients 5.1 Key roles in the carbon cycle Leaf decomposition, as an important link in the carbon cycle of the ecosystem, undertakes the dual function of returning the carbon fixed by plants to the atmosphere and soil (Friedlingstein et al., 2020). On the one hand, during the decomposition of fallen leaves, the respiration of microorganisms oxidizes organic carbon into carbon dioxide (CO₂) and releases it into the atmosphere, which is a major component of heterotrophic respiration in terrestrial ecosystems. On the other hand, the decomposition of fallen leaves transfers a portion of carbon to the soil and retains it for a long time, forming a soil organic carbon pool, which is an important mechanism for carbon sequestration in terrestrial ecosystems (Prescott and Vesterdal, 2021). The decomposition of fallen leaves returns a large amount of organic carbon to the atmosphere through heterotrophic respiration, which is an important carbon source process in the global carbon cycle. At the same time, it also stores part of the carbon in the soil through the formation of humus, which is an important process for maintaining terrestrial carbon sinks. This "dual identity" highlights the indispensable position and complex role of leaf decomposition in the carbon cycle. 5.2 Release and reuse of nutrients such as nitrogen and phosphorus The process of leaf decomposition plays a core role in the cycling of essential nutrient elements such as nitrogen and phosphorus in terrestrial ecosystems. Its main contribution lies in the decomposition and release of organic nutrients into inorganic forms for plants to reuse. Take the nitrogen cycle as an example: Plants absorb inorganic nitrogen (NH₄⁺, NO₃⁻) from the soil and assimilate it into organic tissues. After the leaves fall off, this nitrogen exists in the form of organic nitrogen in the fallen leaves (such as proteins, nucleic acids, etc.) (De Carvalho et al., 2024). Leaf decomposition is the engine of the nitrogen and phosphorus cycles in terrestrial ecosystems: it breaks the closed state of organic nutrients, reconverts nutrients into forms that plants can utilize, and regulates the slow-release and preservation of nutrients through humus (Chen et al., 2020). Without adequate decomposition of fallen leaves, soil nutrients will soon be locked up as the fallen leaves accumulate, and plant growth will be restricted due to the lack of effective nutrients. 5.3 Decomposition and plant nutrient feedback The process of leaf decomposition is not only a one-way nutrient release process, but also forms a feedback loop with the nutrient strategies of plants and community succession. Plants affect the decomposition rate and nutrient release by generating leaves with different characteristics, thereby altering the soil fertility environment. This environment, in turn, influences the growth and competitiveness of the plants themselves and their offspring. This phenomenon is often referred to as "plant-soil feedback" in ecology, where leaf decomposition and nutrient cycling are key links (Dinesha and Dey, 2023). There is a close feedback relationship between the decomposition of fallen leaves and the utilization of plant nutrients: plants affect decomposition, and decomposition in turn affects plants. This feedback ensures that most natural ecosystems can internally circulate nutrients and maintain the dynamic balance of the plant-soil system, and it is also one of the important driving forces for community succession and species replacement (Xu et al., 2020; Casanova-Lugo et al., 2024). 6 Six Cases of Regional and Ecosystem Differences 6.1 Characteristics of leaf decomposition in temperate forests The deciduous decomposition of temperate forests has a moderate rate and a significant seasonal rhythm, which is related to the mild climate and obvious seasonal variations in temperate regions (Zhang et al., 2021). In temperate regions, the litter decomposition rate of arbuloidal mycorrhizal (AM) tree species is faster than that of ectomycorrhizal (ECM) tree species. Among them, the nitrogen content of litter and phylogeny are key predictors (Figure 2) (Keller and Phillips, 2018). Take a typical temperate deciduous broad-leaved forest as an example. Every autumn, a large number of leaves fall and accumulate on the surface of the forest land, and the peak of decomposition usually occurs in the following summer. However, as spring and summer come and temperatures
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 12 rise and precipitation increases, microorganisms and soil animals become active, and a large number of fallen leaves left over from the previous year are rapidly decomposed within a few months. One notable feature is that the Litter layer in temperate forests is more prominent: due to the accumulation of a large amount of seasonal fallen leaves in autumn and winter, a layer of dead leaves several centimeters thick often forms in spring to cover the ground. Studies have shown that deciduous piles mixed with multiple tree species in temperate forests often produce positive mixing effects, that is, the overall decomposition rate is higher than the average value of each individual species. The reasons include that microorganisms obtain nutritional complementarity after the mixture of nitrogen-rich leaves and carbon-rich leaves (Liu et al., 2020). Therefore, creating mixed forests is conducive to improving the efficiency of leaf decomposition and nutrient cycling. Figure 2 Global distribution of leaf litter decay rate (k) observations included in our dataset (Adopted from Keller and Phillips, 2018) Image caption: Yellow dots, leaf litter from arbuscular mycorrhizal (AM)-associated trees; red dots, leaf litter from ectomycorrhizal (ECM)-associated trees (Adopted from Keller and Phillips, 2018) 6.2 Mechanism of high decomposition rate in tropical rainforests Tropical rainforests are renowned for their extremely high rate of leaf decomposition and almost no accumulation of fallen leaves. In a typical tropical humid rainforest ecosystem, dead branches and fallen leaves are often completely decomposed within a few months after falling, and it is difficult to see a thick layer of dead leaves on the surface (Wu et al., 2025). The high decomposition rate of tropical rainforests can be attributed to the effects of three aspects: the high-temperature and high-humidity environment, the high nutrient content of fallen leaves, and the extremely rich and active decomposition biological community. Tropical rainforests thus achieve a high-speed nutrient cycle, ensuring the huge demand for nutrients from dense vegetation. However, this also means that once forests disappear or the amount of litter decreases, the nutrient cycle will be disrupted and soil fertility will drop sharply. This is one of the reasons why the land rapidly becomes infertile after slash-and-burn farming in tropical regions, as there are no fallen leaves to decompose and replenish nutrients (Santiago, 2007; Silva et al., 2018). 6.3 Reasons for the slow decomposition rate in arid and cold regions In sharp contrast to tropical rainforests, the rate of leaf decomposition in arid regions and high-latitude cold areas is extremely slow, and the fallen leaves accumulate on the ground throughout the year. This is mainly attributed to the harsh climatic conditions that impose strong restrictions on the decomposition process. In arid and semi-arid environments (such as desert steppes and savannas), water shortage is the primary limiting factor for decomposition. The fundamental reason for the slow decomposition of fallen leaves in arid and cold regions lies in the unfavorable temperature and humidity conditions, which greatly limit the activity of decomposing organisms. Coupled with the fact that fallen leaves contain a large amount of self-defense substances, these two factors lead to a low decomposition rate and the accumulation of organic matter. This phenomenon reminds us that
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 13 when studying the global material cycle, we need to consider the restrictive effects of different regional environments on decomposition, as well as the potential release risks of huge carbon pools in these regions (Liu et al., 2018; Zhao et al., 2025). 7 Decomposition and Nutrient Cycling Changes in the Context of Global Change 7.1 Dual effects of climate warming on the decomposition process Global warming is believed to have a complex and dual impact on the decomposition process of fallen leaves, which may either accelerate decomposition or inhibit it under certain conditions (Schwieger et al., 2025). On the one hand, an increase in temperature usually enhances the metabolic activity of microorganisms and soil animals, so it is predicted that the overall decomposition rate will rise. This is particularly evident in temperature-constrained regions such as high latitudes and high altitudes: warming can extend the effective decomposition period and increase the peak decomposition rate, accelerating the originally slow process of leaf decomposition (Wu et al., 2025). On the other hand, warming is often accompanied by other environmental changes, such as variations in soil moisture conditions, thereby exerting an inhibitory effect on decomposition. In warm and slightly arid regions, temperature rise will intensify evaporation, leading to soil dryness. Microorganisms, under water stress, will instead become less active and their decomposition rate may decrease (Schwieger et al., 2025). 7.2 The influence of fallen leaves of alien species on the decomposition process Invasive alien plants often have a profound impact on the decomposition process and nutrient cycling through their deciduous properties and interactions with indigenous decomposed food webs. The fallen leaves of some invasive plants decompose rapidly and release nutrients quickly, thereby increasing the nutrient cycling rate of the local area. Some others may contain inhibitory chemicals or extremely low-quality fallen leaves, which slow down the decomposition rate of fallen leaves from native species and alter soil nutrient dynamics (Hu et al., 2022). Invasive alien plants can significantly accelerate or slow down the decomposition process through changes in the quantity and quality of their fallen leaves, and lead to a "redistribution" or "imbalance" in the nutrient cycle. These effects often further feedback to promote the invasion or affect the resilience of the ecosystem, which is an important manifestation of the impact of biological invasion on ecosystem functions. 7.3 Interference of land use change on the input and decomposition environment of fallen leaves The changes in human land use patterns (such as deforestation, agricultural reclamation, urbanization, etc.) have profoundly affected the input volume and decomposition environment of fallen leaves, thereby disrupting the original nutrient cycling pattern of the ecosystem. Land use patterns have an impact on the decomposition process of fallen leaves from three aspects: vegetation, microclimate and soil organisms. If human interference leads to a reduction in the input of fallen leaves or the environment is not conducive to decomposition, the nutrient cycling within the ecosystem will weaken, and it will have to rely on artificial fertilization to maintain productivity. This is reflected in agricultural systems as a case in point. In the protection and restoration of natural ecosystems, efforts should be made to maintain or rebuild the natural environment for the input and decomposition of litter. For instance, when restoring felled areas, it is necessary to allow the retention of dead branches and fallen leaves in the forest and promote their decomposition to restore soil fertility (Li et al., 2023); In urban greening, it is also possible to try "covering with broken leaves on the spot" to reduce the loss of nutrients during cleaning. 8 Concluding Remarks The decomposition of fallen leaves is a core link in the material cycle of terrestrial ecosystems. Through decomposition, carbon and nutrients continuously circulate between plants and soil, not only providing a continuous source of nutrients for vegetation renewal, but also shaping soil structure and enhancing its fertility. Ecosystems in different regions show significant differences in decomposition rates. Tropical rainforests decompose rapidly, while cold or arid regions do so slowly. These differences are jointly determined by water and heat conditions as well as community composition. Decomposer communities play a key role in leaf decomposition. Microorganisms, especially fungi, are mainly responsible for the chemical degradation of complex organic matter, while invertebrates promote the decomposition process through physical crushing and feeding.
International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 206-216 http://ecoevopublisher.com/index.php/ijmec 2 14 The two complement each other, making the decomposition process more efficient. Environmental conditions set boundaries for this process. Macroscopic factors such as temperature and humidity determine the overall rate, while soil pH and nutrient levels affect microbial activity, thereby causing differences among various habitats. Entering the 21st century, climate warming and land use changes have brought new challenges to decomposition and nutrient cycling. High-latitude regions need to be vigilant against the risk of carbon release brought about by the accelerated decomposition of permafrost, while in arid areas, decomposition may be restricted and organic matter accumulation may occur due to warming and reduced precipitation. Meanwhile, the invasion of alien plants significantly affects nutrient cycling by altering the properties of fallen leaves and the communities of decomcaters. Human factors such as excessive removal of litter and monoculture can also reduce the self-nutrient cycling capacity of an ecosystem. Future research should rely on long-term positioning monitoring and multi-factor control experiments to systematically evaluate the combined effects of temperature, precipitation, nitrogen deposition and CO₂ concentration, etc., in order to be closer to the real global change scenario. Technological progress has provided new paths for revealing the decomposition mechanism. Metagenomics can characterize the decomposition of microbial communities and functional gene changes, transcriptome and proteome techniques can analyze the expression of key enzymes at different stages, and metabolomics can track the dynamic changes of compounds during the degradation of organic matter. The integration of multi-omics helps answer the core questions of "who is at work, what has been done, and what products have been produced". For instance, studies on the fallen leaves of poplar trees have revealed the replacement of the dominant microbial community and its association with the carbon and nitrogen cycles. In the future, if such methods can be extended to complex field systems, they will better explain how environmental factors regulate decomposition efficiency and nutrient cycling pathways through decomposer communities, providing theoretical support and practical means for ecological restoration and global change response. Acknowledgments EcoEvo Publisher extends sincere thanks to two anonymous peer reviewers for their feedback on the manuscript. Conflict of Interest Disclosure The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. 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