The impact of abiotic and biotic factor on the soil microbial processes regulating organic matter decomposition

This thesis investigates the impact of abiotic and biotic factors on soil enzyme activity, OM decomposition, and CUE. Specifically, the incorporation of straw into soil creates a hotspot for soil enzyme activity, known as the detritusphere, which enhances enzyme activities in both the rhizosphere and soil profile. However, homogenized straw incorporation intensifies nutrient competition between microorganisms and roots, thereby limiting plant performance. In addition, soils subjected to dry-rewetting cycles trigger microbial activity recovery, while flooding primarily affects enzyme synthesis. Moreover, the symbiosis between plants and AMF creates favorable microsites, enhancing glucose release and enzyme activities in the rhizosphere and mycorrhizosphere, which aids resistance to drought stress. The nutrient demands of different plant species influence the impact of AMF on enzyme activity characteristics in the rhizosphere. Furthermore, salinity negatively affects soil respiration and microbial growth, particularly under conditions of warming or OM input, with labile substrates exacerbating these negative effects. The dynamics of enzyme activity and microbial CUE correlate with microbial growth stages. Labile carbon substrates are more readily utilized by soil microbes compared to recalcitrant ones, and their presence can accelerate the decomposition of recalcitrant carbon substrates in soil.

This thesis demonstrates the variable effects of multiple abiotic and biotic factors on soil enzyme activity and organic matter decomposition through soil incubation experiments, 2D imaging, and soil sample measurements. The importance of multi-factor interactions on soil microbial processes, enzymatic mobilization, and organic matter decomposition is emphasized. Further studies are suggested to focus on modeling the effects of abiotic and biotic factors on soil processes and predicting potential outcomes under changing climatic conditions.

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