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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >The immediate and prolonged effects of climate extremes on soil respiration in a mesic grassland
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The immediate and prolonged effects of climate extremes on soil respiration in a mesic grassland

机译：极端气候对湿地草原土壤呼吸的即时和长期影响

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The predicted increase in the frequency and intensity of climate extremes is expected to impact terrestrial carbon fluxes to the atmosphere, potentially changing ecosystems from carbon sinks to sources, with positive feedbacks to climate change. As the second largest terrestrial carbon flux, soil CO_2 efflux or soil respiration (Rs) is strongly influenced by soil temperature and moisture. Thus, climate extremes such as heat waves and extreme drought should have substantial impacts on Rs. We investigated the effects of such climate extremes on growing season R_s in a mesic grassland by experimentally imposing 2 years of extreme drought combined with midsummer heat waves. After this 2 year period, we continued to measure R_s during a recovery year. Two consecutive drought years reduced R_s by about 25% each growing season; however, when normal rainfall returned during the recovery year, formerly droughted plots had higher rates of R_s than control plots (up to +17%). The heat wave treatments had no effect on Rs, alone or when combined with drought, and during the growing season, soil moisture was the primary driver of R_s with little evidence for R_s temperature sensitivity. When compared to aboveground net primary production, growing season R_s was much less sensitive to drought but was more responsive postdrought. These results are consistent with the hypothesis that ecosystems become sources of CO_2 during drought because carbon inputs (production) are decreased relatively more than outputs (respiration). Moreover, stimulation of R_s postdrought may lengthen the time required for net carbon exchange to return to predrought levels.
机译：预计极端气候的频率和强度的增加将影响陆地向大气的碳通量，可能会改变生态系统，从碳汇到碳源，并对气候变化产生积极反馈。作为第二大的陆地碳通量，土壤CO_2的外流或土壤呼吸（Rs）受到土壤温度和湿度的强烈影响。因此，诸如热浪和极端干旱之类的极端气候将对卢比产生实质性影响。我们通过实验性地施加了2年的极端干旱与盛夏的热浪相结合的方法，研究了这种极端气候对中型草原生长期R_s的影响。在这两年之后，我们在恢复年继续测量R_s。连续两个干旱年份使每个生长季的R_s降低约25％;但是，当恢复年恢复正常降雨时，以前干旱的地块的R_s率高于对照地块（高达+ 17％）。热浪处理单独或与干旱结合时对Rs没有影响，并且在生长季节，土壤水分是R_s的主要驱动力，几乎没有证据表明R_s对温度敏感。与地上净初级生产力相比，生长期R_s对干旱的敏感性要低得多，但干旱后的响应能力更强。这些结果与以下假设一致：在干旱期间，生态系统成为CO_2的来源，因为碳输入（生产）的减少幅度相对于产出（呼吸）的减少幅度更大。此外，对R_s后干旱的刺激可能会延长净碳交换返回到干旱前水平所需的时间。

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