Institute for Genomic Biology, University of Illinois, Urbana, IL 61801, USA.
Glob Chang Biol. 2013 May;19(5):1572-84. doi: 10.1111/gcb.12155. Epub 2013 Mar 5.
Maize, in rotation with soybean, forms the largest continuous ecosystem in temperate North America, therefore changes to the biosphere-atmosphere exchange of water vapor and energy of these crops are likely to have an impact on the Midwestern US climate and hydrological cycle. As a C4 crop, maize photosynthesis is already CO2 -saturated at current CO2 concentrations ([CO2 ]) and the primary response of maize to elevated [CO2 ] is decreased stomatal conductance (gs ). If maize photosynthesis is not stimulated in elevated [CO2 ], then reduced gs is not offset by greater canopy leaf area, which could potentially result in a greater ET reduction relative to that previously reported in soybean, a C3 species. The objective of this study is to quantify the impact of elevated [CO2 ] on canopy energy and water fluxes of maize (Zea mays). Maize was grown under ambient and elevated [CO2 ] (550 μmol mol(-1) during 2004 and 2006 and 585 μmol mol(-1) during 2010) using Free Air Concentration Enrichment (FACE) technology at the SoyFACE facility in Urbana, Illinois. Maize ET was determined using a residual energy balance approach based on measurements of sensible (H) and soil heat fluxes, and net radiation. Relative to control, elevated [CO2 ] decreased maize ET (7-11%; P < 0.01) along with lesser soil moisture depletion, while H increased (25-30 W m(-2) ; P < 0.01) along with higher canopy temperature (0.5-0.6 °C). This reduction in maize ET in elevated [CO2 ] is approximately half that previously reported for soybean. A partitioning analysis showed that transpiration contributed less to total ET for maize compared to soybean, indicating a smaller role of stomata in dictating the ET response to elevated [CO2 ]. Nonetheless, both maize and soybean had significantly decreased ET and increased H, highlighting the critical role of elevated [CO2 ] in altering future hydrology and climate of the region that is extensively cropped with these species.
玉米与大豆轮作，构成了北美温带地区最大的连续生态系统，因此这些作物对水蒸汽和能量的生物群落-大气交换的改变，很可能对美国中西部的气候和水文循环产生影响。作为一种 C4 作物，玉米的光合作用在当前的二氧化碳浓度 ([CO2]) 下已经达到 CO2 饱和，而玉米对高浓度 CO2 的主要反应是气孔导度（gs）降低。如果在高浓度 CO2 下玉米的光合作用没有受到刺激，那么气孔导度的降低不会被更大的冠层叶面积所抵消，这可能导致相对于先前报道的 C3 物种大豆的蒸散量更大的减少。本研究的目的是量化高浓度 CO2 对玉米（Zea mays）冠层能量和水分通量的影响。2004 年和 2006 年，玉米在伊利诺伊州厄巴纳市的 SoyFACE 设施中使用自由空气浓度富集（FACE）技术，在大气和高浓度 CO2（550 μmol mol-1）下生长，2010 年为 585 μmol mol-1。利用基于感热（H）和土壤热通量以及净辐射测量的剩余能量平衡方法，确定了玉米的蒸散量。与对照相比，高浓度 CO2 降低了玉米的蒸散量（7-11%；P<0.01），同时土壤水分消耗减少，而 H 增加（25-30 W m-2；P<0.01），同时冠层温度升高（0.5-0.6°C）。与先前报道的大豆相比，高浓度 CO2 下玉米蒸散量的减少约为一半。分配分析表明，与大豆相比，玉米蒸腾作用对总蒸散量的贡献较小，这表明气孔在决定蒸散对高浓度 CO2 的响应方面的作用较小。尽管如此，玉米和大豆的蒸散量都显著减少，H 增加，这突出表明高浓度 CO2 在改变该地区广泛种植这些物种的未来水文学和气候方面发挥着关键作用。
