Footnote:
Diese Datenquelle enthält auch Bestandsnachweise, die nicht zu einem Volltext führen.
Description:
Agricultural soils are important C reservoirs that influence global climate change. Plants modulate the soil environment by reduced C release from their roots or through rapid nutrient uptake from the soil by their related microorganisms. Microbial metabolic functions (catabolic and anabolic) are essential control valves for soil organic matter (SOM) turnover and also an essential factor in increasing agricultural soil productivity and decelerated increase in atmospheric CO2 concentration. However, studies on C and nutrient cycling mostly focus on the effect of organic matter input but rarely combined with their microbial metabolic processes (catabolic and anabolic pathways) in SOM turnover. In this thesis, I have investigated the microbial metabolic processes involved in organic matter decomposition, transformation, and accumulation in agricultural soils, depending on the impact of substrate-nutrient stoichiometry ratios (such as C/N ratios) of organic compounds and the type of organic matter (such as labile root exudates and lignin). This overarching research goal has been explored in three different experiments. In the first experiment, I investigated the effect of different C/N ratios with low molecular weight and labile plant-derived organic matter (such as root exudates) on microbial activities. I incubated a paddy field soil with three artificial root exudates characterized by different C/N ratios (CN6, CN10, and CN80) using a mixture of glucose, oxalic acid, and alanine. In the second experiment, I focused on the microbial degradation of a complex plant biomacromolecule (lignin), which is considered stable particularly under anaerobic conditions. I incubated the soil for 365 days to investigate the microbial degradation of lignin (13C lignin >98 atom%, 80% chemical purity) under anaerobic, followed by aerobic, conditions at different time intervals. While the first two studies dealt with short- and intermediate-term incubation experiments, in a third experiment, I focused on soil samples collected ...