Knowledge of soil respiration and photosynthesis under elevated CO2 is crucial for exactly understanding and predicting the carbon balance in forest ecosystems in a rapid CO2-enriched world. Quercus mongolica Fischer ex Ledebour seedlings were planted in open-top chambers exposed to elevated CO2 (EC = 500 µmol mol−1) and ambient CO2 (AC = 370 µmol mol−1) from 2005 to 2008. Daily, seasonal and inter-annual variations in soil respiration and photosynthetic assimilation were measured during 2007 and 2008 growing seasons. EC significantly stimulated the daytime soil respiration by 24.5% (322.4 at EC vs. 259.0 mg CO2 m−2 hr−1 at AC) in 2007 and 21.0% (281.2 at EC vs. 232.6 mg CO2 m−2 hr−1 at AC) in 2008, and increased the daytime CO2 assimilation by 28.8% (624.1 at EC vs. 484.6 mg CO2 m−2 hr−1 at AC) across the two growing seasons. The temporal variation in soil respiration was positively correlated with the aboveground photosynthesis, soil temperature, and soil water content at both EC and AC. EC did not affect the temperature sensitivity of soil respiration. The increased daytime soil respiration at EC resulted mainly from the increased aboveground photosynthesis. The present study indicates that increases in CO2 fixation of plants in a CO2-rich world will rapidly return to the atmosphere by increased soil respiration.
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机译：在二氧化碳迅速增加的世界中，了解二氧化碳水平升高下的土壤呼吸和光合作用对于准确了解和预测森林生态系统中的碳平衡至关重要。将Ledebour的蒙古栎Fischer幼苗种植在暴露于升高的CO2（EC = 500μmolmol -1 ）和环境CO2（AC = 370μmolmol -1 ）从2005年到2008年。在2007年和2008年的生长季节期间，测量了土壤呼吸和光合同化的每日，季节性和年际变化。 EC在2007年显着刺激了白天土壤呼吸，增幅为24.5％（EC时为322.4，而AC时为259.0 mg CO2 m -2 hr -1 ）和21.0％（281.2时）相对于2008年EC的232.6 mg CO2 m −2 hr -1 （AC），白天的二氧化碳吸收量增加了28.8％（EC时为624.1 vs. 484.6 mg CO2在两个生长季节中，m −2 hr −1 在AC）。 EC和AC上土壤呼吸的时间变化与地上光合作用，土壤温度和土壤含水量呈正相关。 EC不会影响土壤呼吸的温度敏感性。 EC白天土壤呼吸的增加主要是由于地上光合作用的增加。本研究表明，在富含CO 2的世界中，植物对CO 2固定的增加将通过增加土壤呼吸而迅速返回大气。
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