Jackson R B, Sala O E, Field C B, Mooney H A
Department of Biological Sciences, Stanford University, 94305, Stanford, CA, USA.
Department of Ecology, Faculty of Agronomy, University of Buenos Aires, Av San Martín 4453, Buenos Aires, Argentina.
Oecologia. 1994 Aug;98(3-4):257-262. doi: 10.1007/BF00324212.
Global atmospheric CO is increasing at a rate of 1.5-2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO in a California annual grassland. Elevated CO led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30-35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discrimination. Increases in CO and photosynthesis resulted in more seeds per plant (30%) and taller and heavier plants (27% and 41%, respectively). Elevated CO also reduced seed N concentrations (9%).
全球大气中的二氧化碳正以每年1.5 - 2 ppm的速度增加，预计到下个世纪末将翻倍。了解陆地生态系统在这种变化的环境中将如何做出反应是当前研究的一个重要目标。在此，我们展示了对加利福尼亚一年生草地中二氧化碳浓度升高进行实地研究的结果。二氧化碳浓度升高导致该草地最常见的物种——野燕麦（Avena barbata Brot.）的叶片气孔导度和蒸腾作用降低（约50%），中午叶片水势升高（30 - 35%）。较高的二氧化碳浓度还导致中午光合速率提高（平均提高70%）。当野燕麦开始出现衰老迹象时，在生长季节末期，二氧化碳对气孔导度和叶片水势的影响减弱。通过瞬时气体交换测量和季节性碳同位素判别估计，在二氧化碳浓度升高的情况下，水分利用效率大约提高了一倍。二氧化碳增加和光合作用增强导致单株种子数量增加（30%），植株更高、更重（分别增加27%和41%）。二氧化碳浓度升高还降低了种子氮浓度（9%）。
