Molecular Microbiology Research 2024, Vol.14, No.2, 79-91 http://microbescipublisher.com/index.php/mmr 83 4.3 pH levels Soil pH is a key factor that influences microbial community composition and activity, thereby affecting decomposition rates. The pH of the soil can alter the availability of nutrients and the activity of decomposing microorganisms. For example, studies have shown that soil pH can significantly impact microbial response during decomposition, with certain pH levels favoring specific microbial communities (Mason et al., 2022). In the context of human decomposition, variations in soil pH were found to be influenced by intrinsic factors such as body mass index (BMI), which in turn affected microbial activity and decomposition rates. Additionally, in aquatic ecosystems, pH levels along with other abiotic factors like temperature and ionic concentration were found to influence microbial decomposition and enzyme activity, further highlighting the importance of pH in decomposition processes (Fenoy et al., 2016). 5 Impact of Microbial Decomposition on Soil Health Microbial decomposition is fundamental to nutrient cycling, soil structure, fertility, and the suppression of soil-borne diseases. The interplay between microbial communities and environmental factors such as nitrogen fertilization, agricultural practices, and fire events significantly impacts soil health and ecosystem functioning. 5.1 Nutrient cycling 5.1.1 Carbon cycle Microbial decomposition plays a crucial role in the carbon cycle by breaking down organic matter and releasing carbon dioxide back into the atmosphere. Soil microbes, including bacteria and fungi, are essential for the transformation and processing of carbon in terrestrial ecosystems. Nitrogen fertilization has been shown to significantly alter soil microbial community composition, which in turn affects soil organic carbon (SOC) turnover and nutrient acquisition (Li et al., 2019; Jia et al., 2020). Additionally, agricultural practices, such as organic and conventional management, influence microbial communities and their ability to decompose crop residues, impacting soil carbon accrual and fertility (Arcand et al., 2016). Fire events also reorganize microbially-mediated nutrient cycles, including carbon, by decreasing soil enzyme activities and microbial biomass (Zhou et al., 2022). 5.1.2 Nitrogen cycle Microbial activity is integral to the nitrogen cycle, facilitating processes such as nitrogen fixation, nitrification, and denitrification. Long-term nitrogen fertilization experiments have demonstrated that nitrogen input significantly modifies both bacterial and fungal community compositions, enhancing the potential for nitrogen acquisition and recalcitrant carbon degradation. However, nitrogen enrichment can decrease microbial biomass and diversity, potentially weakening the linkage between soil carbon and microbial diversity, which is critical for maintaining ecosystem services (Yang et al., 2022). In tropical forests, nitrogen limitation alongside phosphorus limitation has been identified as a key factor affecting microbial processes and soil health (Camenzind et al., 2018). 5.1.3 Phosphorus cycle Phosphorus is another essential nutrient cycled by soil microbes. Studies have shown that phosphorus limitation is prevalent in tropical forests, significantly affecting microbial biomass and process rates (Camenzind et al., 2018). Fire events can decrease soil phosphorus-acquiring enzyme activities but increase available phosphorus through pyro-mineralization, altering the phosphorus cycle (Zhou et al., 2022). In paddy soils, the addition of biogas slurry has been found to shift microbial phosphorus-transformation communities, highlighting the importance of microbial mediation in phosphorus cycling (Wang et al., 2021). 5.2 Soil structure and fertility Microbial decomposition directly influences soil structure and fertility by breaking down organic matter and contributing to the formation of soil aggregates. The activity of soil microbes and their extracellular enzymes is crucial for maintaining soil physical and chemical properties. Nitrogen enrichment, for example, has been shown
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