Department of Forest Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
PLoS One. 2010 Dec 6;5(12):e15134. doi: 10.1371/journal.pone.0015134.
Knowledge of soil respiration and photosynthesis under elevated CO(2) is crucial for exactly understanding and predicting the carbon balance in forest ecosystems in a rapid CO(2)-enriched world. Quercus mongolica Fischer ex Ledebour seedlings were planted in open-top chambers exposed to elevated CO(2) (EC = 500 µmol mol(-1)) and ambient CO(2) (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 CO(2) m(-2) hr(-1) at AC) in 2007 and 21.0% (281.2 at EC vs. 232.6 mg CO(2) m(-2) hr(-1) at AC) in 2008, and increased the daytime CO(2) assimilation by 28.8% (624.1 at EC vs. 484.6 mg CO(2) 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 CO(2) fixation of plants in a CO(2)-rich world will rapidly return to the atmosphere by increased soil respiration.
在 CO2 浓度升高的世界中，了解土壤呼吸和光合作用对于准确理解和预测森林生态系统的碳平衡至关重要。2005 年至 2008 年，在开顶式气室中种植了蒙古栎（Quercus mongolica Fischer ex Ledebour）幼苗，这些气室分别暴露于高浓度 CO2（EC = 500 µmol mol-1）和大气 CO2（AC = 370 µmol mol-1）环境中。在 2007 年和 2008 年的生长季节中，测量了土壤呼吸和光合作用同化的日变化、季节变化和年际变化。2007 年，EC 显著刺激了白天的土壤呼吸，使其增加了 24.5%（EC 为 322.4 mg CO2 m-2 hr-1，AC 为 259.0 mg CO2 m-2 hr-1），2008 年增加了 21.0%（EC 为 281.2 mg CO2 m-2 hr-1，AC 为 232.6 mg CO2 m-2 hr-1）。在这两个生长季节中，EC 使白天的 CO2 同化增加了 28.8%（EC 为 624.1 mg CO2 m-2 hr-1，AC 为 484.6 mg CO2 m-2 hr-1）。土壤呼吸的时间变化与地上光合作用、土壤温度和土壤水分含量在 EC 和 AC 下均呈正相关。EC 不影响土壤呼吸的温度敏感性。EC 下白天土壤呼吸的增加主要归因于地上光合作用的增加。本研究表明，在 CO2 丰富的世界中，植物固定 CO2 的增加将通过增加土壤呼吸迅速返回大气。
