温度和UV-B辐射增加对水稻根系分泌物和土壤氮转化的影响OA

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.