Molecular Soil Biology 2024, Vol.15, No.3, 99-108 http://bioscipublisher.com/index.php/msb 103 The microbial community structure is also a vital indicator of soil health influenced by leaf litter. Studies have shown that the addition of leaf litter can alter the composition and functional characteristics of soil microbial communities. For example, the decomposition of leaf litter from dominant tree species enhances the metabolic capacity and functional diversity of soil microbes, which is crucial for soil health and forest succession (Liang et al., 2015). Moreover, the presence of specific microbial taxa, such as nitrifying and nitrogen-fixing bacteria, can be indicative of the nutrient status and overall health of the soil (Tanikawa et al., 2022). 5.2 Role in disease suppression and plant health Leaf litter not only contributes to soil health but also plays a significant role in disease suppression and plant health. The decomposition of leaf litter can lead to the release of various organic compounds and nutrients that enhance soil microbial activity and diversity, which in turn can suppress soil-borne pathogens. For instance, the addition of leaf litter has been shown to increase the ATP-to-microbial biomass C ratio and the ergosterol-to-microbial biomass C ratio, indicating a more active and diverse microbial community capable of outcompeting pathogenic organisms (Salamanca et al., 2006). Furthermore, the presence of a diverse microbial community in the soil, fostered by leaf litter decomposition, can enhance plant health by promoting beneficial symbiotic relationships and improving nutrient availability. The increased microbial diversity and activity can lead to better nutrient cycling and availability, which supports plant growth and resilience against diseases (Dong et al., 2021). Additionally, the specific composition of leaf litter, such as the carbon-to-nitrogen ratio and lignin content, can influence the microbial community structure and its ability to suppress plant pathogens (Naimei, 2011). In summary, leaf litter significantly influences soil health indicators and plays a vital role in disease suppression and plant health by enhancing soil microbial diversity and activity. The decomposition of leaf litter from various tree species contributes to nutrient cycling, improves soil physicochemical properties, and fosters a diverse microbial community that supports healthy plant growth and resilience against diseases (Liang et al., 2015; Dong et al., 2021). 6 Case Studies 6.1 Effects of leaf litter on soil fertility in temperate forests Leaf litter plays a crucial role in maintaining soil fertility in temperate forests. The decomposition of leaf litter releases essential nutrients back into the soil, which are vital for plant growth. For instance, the leachates from broadleaf litter in temperate forests contain higher amounts of carbon and nitrogen, which significantly enhance soil microbial activity and respiration, leading to improved soil fertility (Joly et al., 2016). Additionally, the diversity of leaf litter can influence the microbial community structure and nutrient cycling, as observed in mixed Quercus acutissima and Robinia pseudoacacia forests in Northern China, where mixed forests showed more stable microbial diversity and better nutrient cycling compared to pure forests (Dong et al., 2021). 6.2 Leaf litter's role in microbial diversity in tropical rainforests In tropical rainforests, leaf litter significantly impacts microbial diversity and function. The identity of leaf litter species, rather than their diversity, has been shown to shape microbial functions and the abundance of soil organisms. For example, in Ecuadorian tropical montane rainforests, leaf litter from species with low carbon-to-nitrogen ratios, such as Cecropia andina, improved microbial activity and increased the abundance of microarthropods (Sánchez-Galindo et al., 2021). Furthermore, the addition of different leaf litter types to tropical forest soils in the Philippines altered soil microbial biomass and energy charge, indicating that leaf litter quality directly influences microbial community dynamics (Salamanca et al., 2006). 6.3 Leaf litter's impact on soil health in boreal forests In boreal forests, leaf litter contributes to soil health by influencing microbial community structure and nutrient availability. The decomposition of leaf litter and deadwood is primarily driven by fungi, which play a significant role in nutrient cycling and maintaining soil health (Bani et al., 2018). However, the impact of leaf litter on microbial biomass and community structure can vary. For instance, a global meta-analysis revealed that
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