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| Effects of elevated temperature and UV-B radiation on rice root exudates and soil nitrogen transformation |
| Received:July 11, 2025 |
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| KeyWord:temperature;UV-B radiation;root exudates;bacteria number;enzyme activity;nitrogen content;N2O |
| Author Name | Affiliation | E-mail | | LI Haitao | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | WU Yonglin | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LIANG Xinran | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | ZHAN Fangdong | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Yuan | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | HE Yongmei | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | heyongmei06@126.com |
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| Abstract: |
| To elucidate the differential effects of elevated temperature and enhanced UV-B radiation on rice root exudates and their mediated soil nitrogen cycling responses under climate change scenarios, a field experiment was conducted in the Yuanyang Terraces(1 600 m above sea level)using the local rice cultivar Baijiao Laojing. The study investigated the impacts of elevated atmospheric temperature (+2.0 ℃)and enhanced UV-B radiation(+5.0 kJ·m-2)on rice root exudates and their subsequent effects on soil nitrogen transformation. The results showed that elevated temperature significantly increased the contents of amino acids, soluble sugars, and low-molecular-weight organic acids(except citric acid)in rice root exudates at the jointing stage, with respective increments of 56.4%, 30.2%, and 24.6%-143.8%. In contrast, enhanced UV-B radiation reduced the content of amino acids(except for amino acids at the tillering stage)and soluble sugars(except for maturity stage), with decreases of 37.3% and 47.7%-62.5%, respectively. Elevated temperature significantly increased the abundance of nitrogen-fixing and nitrifying bacteria, enhanced nitrate reductase activity, and raised the soil soluble organic nitrogen(SON)content. Conversely, enhanced UV-B radiation reduced the population of denitrifying bacteria and decreased N2O emission flux. Both elevated temperature and UV-B radiation treatments increased the abundance of nitrogen-fixing bacteria and SON content. Mantel test analysis revealed a significant positive correlation between nitrogen-fixing bacteria and SON(P<0.05), as well as a highly significant positive correlation between nitrifying bacteria and N2O emission flux(P<0.001). The study demonstrates that elevated temperature increases amino acid and soluble sugar contents in root exudates, thereby enhancing the population of nitrogen-fixing bacteria and subsequently promoting biological nitrogen fixation. Conversely, enhanced UV-B radiation suppresses denitrifying bacterial populations and attenuates the denitrification process, leading to reduced N2O emissions. The synergistic interaction between these factors creates a "nitrogen fixation promotion-emission reduction" effect, which simultaneously increases soil soluble organic nitrogen content while decreasing N2O emissions. |
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