Energy balance and water use efficiency of rice canopies under free-air CO2 enrichment
Energy balance and water use efficiency of rice canopies under free-air CO2 enrichment
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DOI：
10.1016/j.agrformet.2005.09.010
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发表时间：
2005-11-10
影响因子：
6.2
通讯作者：
Kobayashi, K
中科院分区：
文献类型：
--
作者：
Yoshimoto, M;Oue, H;Kobayashi, K
为了预测农业生产力和水资源的可获得性，必须评估由于CO_2浓度升高而引起的作物水分利用的变化。我们量化了升高的[CO2]对稻田能量平衡和冠层蒸散(ET)的影响。水稻(Oryza sativa L.)是在日本北部自由空气二氧化碳浓缩(FACE)施加的环境[CO2](A-CO2)和高[CO2](E-CO2)下生长的。观测了微气象和植物特征，包括气孔导度和叶面积指数(LAI)。我们使用双源模型估计能量平衡，包括植被冠层和水面的热量传输，以避免由于测量的辐射红外(IR)温度的不确定性而产生的误差。在颗粒起始阶段，E-CO使上部叶片气孔导度降低13%，下部叶片气孔导度降低40%，但随后降低。在E-CO图中，随着水汽压差的增加，气孔关闭得更多。在E-CO2下，由于气孔关闭，植被冠层的日平均温度上升了0.2-1摄氏度，而水稻抽穗前的水面温度下降了1摄氏度，这是因为在E-CO2中较大的叶片增加了遮荫。6月份之前，E-CO的辐射红外温度下降了1摄氏度，之后又上升了0.6摄氏度。E-CO潜热通量减少，感热通量增加和长波辐射上升抵消了潜热通量的下降。干旱多风条件下降幅最大。植物在整个生长季节的总用水量在A-CO_2中为268.7毫米，在E-CO_2中为246.8朗姆，在E-CO_2中节省了22毫米水。蒸腾作用减少(8.2%)，总生物量增加(9.1%)，E-CO2水分利用效率提高19%。(C)2005 Elsevier B.V.保留所有权利。
Changes in crop water use due to elevated CO, concentration ([CO2]) must be evaluated for predicting agricultural productivity and water resource availability. We quantified the effects of elevated [CO2] on the energy balance and canopy evapotranspiration (ET) in rice paddies. Rice (Oryza sativa L.) was grown under both ambient [CO2] (A-CO2) and elevated [CO2] (E-CO2) imposed by free-air CO2 enrichment (FACE) in northern Japan. Observations were made of micrometeorology and plant characteristics, including stomatal conductance and leaf area index (LAI). We estimated energy balances using a double-source model with heat transfers from the vegetation canopy and the water surface to avoid errors due to uncertainty in the measured radiative infrared (IR) temperatures. E-CO, reduced stomatal conductance by 13% in upper leaves and by 40% in lower leaves at the particle initiation stage, but the reduction rates subsequently decreased. Stomata closed more in the E-CO, plot as vapour pressure deficit increased. Daily mean temperature of the vegetation canopy increased by 0.2-1 degrees C in response to stomatal closure under E-CO2, whereas water surface temperature decreased by 1 degrees C before rice heading because of increased shading from the larger leaves in E-CO2. The radiative IR temperature decreased by up to 1 degrees C in E-CO, before June, and increased by up to 0.6 degrees C thereafter. Latent heat flux decreased in E-CO,, which was balanced by increased sensible heat flux and upward long-wave radiation. The decrease was greatest under dry and windy conditions. Total water use by plants throughout the growing season was 268.7 mm in A-CO2 and 246.8 rum in E-CO2, giving a saving of 22 mm of water in E-CO2. Reduced transpiration (by 8.2%), combined with increased total biomass (by 9.1%), increased water use efficiency in E-CO2 by 19%. (c) 2005 Elsevier B.V. All rights reserved.