VARIABILITY IN THE TEMPERATURE SENSITIVITY OF ANOXIC ORGANIC MATTER DECOMPOSITION

Temperature sensitivity is a key feature of microbial processes that regulates biological carbon emissions in natural environments. This feature is commonly quantified as Q₁₀, the rate change over a temperature interval of 10 °C [1]. Here we apply biogeochemical modeling to analyze the temperature sensitivity of anerobic degradation of organic matter and its dependence on substrate concentrations, biomass abundance, and microbial interactions. We first carry out a meta-analysis of Q₁₀ values determined previously, and the results show that cold areas such as arctic and tundra soils can have higher Q₁₀ values reaching over 200, wherase in temperate and tropical areas, the Q₁₀ values range from as small as 1.5 to near 3.5. We then simulate the anaerobicdegradation of butyrate, a key intermediate of organic matter decomposition, at temperatures ranging from 5 to 50 ℃ in a closed environment. We also simulate the anaerobic degradation of natural organic matter acorss the different temperatures in a semi-open enviroment. Our modeling-derived Q₁₀ values vary from 1 to over 400, within the ranges reported by previous laboratory and field experiments [2,3]. The results show that the temperature sensitivity tend to be larger at lower temperatures, and can be accounted for by the concurrent responses of reaction thermodynamics and biomass concentrations. In addition, the Q₁₀ values are also shaped by biogeochemical conditions, including substrate concentrations and microbial interactions. These results suggest that Q₁₀ might not always capture the complexity of temperature sensitivity of biogeochemical processes, and its application deserves additional considerations of how different environmental factors work together in determining the kinetics of biogeochemical processes.

References:

[1] Hamdi, S., et al., 2013. Soil Biology and Biochemistry, 58, pp.115-126.

[2] Bracho, R., et al., 2016. Soil Biology and Biochemistry, 97, pp.1-14.

[3] Gutiérrez-Girón, A., et al., 2015. Geoderma, 237, pp.1-8.