Dissolved organic matter is an important component of carbon biogeochemical cycling processes, closely related to various ecosystem functions such as organic carbon decomposition. The spatial pattern and driving mechanism of organic carbon decomposition characteristics in lake sediments under the background of climate warming are still unclear, which hinders the evaluation of lake carbon sink function under the warming background and accurate prediction of future climate change.

Wang Jianjun, a researcher at the Nanjing Institute of Geography and Lakes, Chinese Academy of Sciences, focused on lakes, rivers and other water bodies as well as other major ecosystems on the earth, integrated 2995 samples of dissolved organic matter worldwide, covering typical climatic regions such as the tropics and tundra permafrost, and comprehensively analyzed the molecular characteristics of two types of dissolved organic matter, namely, the "hydrogen/carbon ratio" and the "oxygen/carbon ratio", namely, the H/C and O/C ratios. Research has shown that in the habitat of land sea continuum, the dissolved organic matter H/C ratio shows snow>glaciers>ocean>freshwater/soil>groundwater. Along the latitude gradient, the H/C ratio exhibits a predictable U-shaped pattern; In rivers, lakes, and forest soils at mid latitudes of 40 ° -50 °, the H/C ratio is the lowest. The H/C and O/C ratios are mainly influenced by environmental factors such as pH, dissolved oxygen, carbon and nitrogen content.

The team collected 50 lakes nationwide and analyzed the decomposition rate and temperature sensitivity of sediment organic carbon Q10. It was found that both the decomposition rate and Q10 showed significant variation; However, no obvious latitude gradient distribution pattern was found at the spatial scale. The decomposition rate of organic carbon is mainly influenced by the organic carbon content, while Q10 is mainly driven by the chemical diversity of dissolved organic matter in sediments. Compared to traditional environmental variables such as climate, physicochemical factors, and microbial communities, the study considers that chemical diversity will increase the explanatory power of Q10 variation by 32.8%, and chemical diversity is the only driving factor with a direct effect.

The above results characterize the spatial distribution pattern of dissolved organic matter at the molecular level, revealing the latitude pattern and driving mechanism of organic carbon decomposition rate and temperature sensitivity in lake sediments. They will help to analyze the stability of lake organic carbon under the background of climate warming and its mediated climate feedback mechanism.

Recently, relevant research results have been published in Fundamental Research and Global Change Biology, respectively. The research work has been supported by the National Natural Science Foundation of China, the Second Comprehensive Scientific Expedition to the Qinghai Tibet Plateau, and the independently deployed projects of the Nanjing Institute of Geography. This study was conducted in collaboration with the Nanjing Institute of Geography, Nanjing University, the Korean Institute of Basic Sciences, and the University of Cambridge in the United Kingdom.

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Spatial pattern of organic carbon decomposition rate and temperature sensitivity in lake sediments