季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲(26.7°N,115.1°E)人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO(Ecological Assimilation of Land and Climate Observation)模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方(R2)及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬(发生较严重干旱胁迫)较2004年同期(干旱程度轻)相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%～60%。模拟与观测结果均表明,2003年7月下旬每天正午的波文比大都介于1～2.2,而2004年同期正午的波文比则介于0.2～0.6。EALCO模型通过Ball模型将植物碳水过程耦合在一起,从而可以很好的模拟植物的气孔行为,进而准确的模拟植物水热过程对干旱的响应。土壤水分匮乏对冠层导度的限制是2003年干旱期间冠层潜热通量模拟值下降的根本原因。
The objective of this study was to analyze the effects of climate change and doubled atmospheric CO2 concentrations, as well as the combined effects of climate change and doubling atmospheric CO2 concentrations on soi...
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The objective of this study was to analyze the effects of climate change and doubled atmospheric CO2 concentrations, as well as the combined effects of climate change and doubling atmospheric CO2 concentrations on soil organic carbon （SOC） in the alpine steppe of the northern Tibetan Plateau using the CENTURY model. The results indicate that SOC loss in climate change scenarios varied from 49.77 52.36% in the top 20 cm. The simulation results obtained for a P1T0 scenario （increased precipitation and unchanged temperature）, POT1 scenario （unchanged precipitation and increased temperature）, and P1T1 scenario （increased precipitation and increased temperature） were similar. The alpine steppe in the P1T1 scenarios lost the greatest amount of SOC （844.40 g C m-2, representing the least amount of SOC） by the end of the simulation. The simulation for POT1 scenarios resulted in a 49.77% loss of SOC. However, SOC increased 12.87% under the COs doubling scenario, compared with the unchanged CO2 scenario. CO2 enhancement effects on SOC were greater than the climate change effects on SOC alone. The simulation of combined climate change and doubling atmospheric CO2 led to a decrease in SOC. This result indicated a decrease of 52.39% in SOC for the P1T1 ＋ 2 × CO2 scenario, 49.81% for the POT1 ＋ 2 ×CO2 scenario, and 52.30% for the P1T0 ＋ 2 ×CO2 scenario over the next 50 years. Therefore, SOC content in the alpine steppe will change because of changes in precipitation, temperature and atmospheric CO2 concentrations.
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