Formation of soil organic carbon pool is regulated by the structure of dissolved organic matter and microbial carbon pump efficacy: A decadal study comparing different carbon management strategies |
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| Authors: | Yalan Chen,Zhangliu Du,Zhe Weng,Ke Sun,Yuqin Zhang,Qin Liu,Yan Yang,Yang Li,Zhibo Wang,Yu Luo,Bo Gao,Bin Chen,Zezhen Pan,Lukas Van Zwieten |
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| Affiliation: | 1. State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, China;2. Beijing Key Laboratory of Biodiversity and Organic Farming, College of Resources and Environmental Sciences, China Agricultural University, Beijing, China;3. School of Agriculture and Food Sciences, The University of Queensland, St. Lucia, Queensland, Australia;4. Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Institute of Soil and Water Resources and Environmental Science, Zhejiang University, Hangzhou, China;5. State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing, China;6. Department of Environmental Science and Engineering, Fudan University, Shanghai, China;7. NSW Department of Primary Industries, Wollongbar Primary Industries Institute, Wollongbar, New South Wales, Australia |
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| Abstract: | To achieve long-term increases in soil organic carbon (SOC) storage, it is essential to understand the effects of carbon management strategies on SOC formation pathways, particularly through changes in microbial necromass carbon (MNC) and dissolved organic carbon (DOC). Using a 14-year field study, we demonstrate that both biochar and maize straw lifted the SOC ceiling, but through different pathways. Biochar, while raising SOC and DOC content, decreased substrate degradability by increasing carbon aromaticity. This resulted in suppressed microbial abundance and enzyme activity, which lowered soil respiration, weakened in vivo turnover and ex vivo modification for MNC production (i.e., low microbial carbon pump “efficacy”), and led to lower efficiency in decomposing MNC, ultimately resulting in the net accumulation of SOC and MNC. In contrast, straw incorporation increased the content and decreased the aromaticity of SOC and DOC. The enhanced SOC degradability and soil nutrient content, such as total nitrogen and total phosphorous, stimulated the microbial population and activity, thereby boosting soil respiration and enhancing microbial carbon pump “efficacy” for MNC production. The total C added to biochar and straw plots were estimated as 27.3–54.5 and 41.4 Mg C ha−1, respectively. Our results demonstrated that biochar was more efficient in lifting the SOC stock via exogenous stable carbon input and MNC stabilization, although the latter showed low “efficacy”. Meanwhile, straw incorporation significantly promoted net MNC accumulation but also stimulated SOC mineralization, resulting in a smaller increase in SOC content (by 50%) compared to biochar (by 53%–102%). The results address the decadal-scale effects of biochar and straw application on the formation of the stable organic carbon pool in soil, and understanding the causal mechanisms can allow field practices to maximize SOC content. |
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| Keywords: | amino sugar bacterial 16S rDNA sequencing enzyme activity ESI-FT-ICR-MS fungal ITS rDNA sequencing microbial carbon pump soil respiration |
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