The critical role of extreme heat for maize production in the United States
The critical role of extreme heat for maize production in the United States
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DOI：
10.1038/nclimate1832
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发表时间：
2013-05-01
影响因子：
30.7
通讯作者：
Schlenker, Wolfram
中科院分区：
文献类型：
--
作者：
Lobell, David B.;Hammer, Graeme L.;Schlenker, Wolfram
对美国（1）和其他地方（2）的玉米产量的统计研究表明了两个明显的特征：对30摄氏度以上的温度积累（或极端度日（EDD））的强烈负产量反应，以及对季节性降雨的相对较弱的反应。在这里，我们表明，基于过程的农业生产系统模拟器（APSIM）是能够重现这两种关系在美国中西部地区，并提供深入了解的基本机制。EDD在APSIM的主要影响与增加的蒸汽压力赤字，这有助于水应力在两个方面：通过增加对土壤水的需求，以维持一定的碳同化率，并通过提高蒸腾速率减少未来的土壤水供应。APSIM将每日水压力计算为水供应与需求的比率，在关键的7月份，这一比率对2摄氏度变暖的反应是对降水量减少20%的反应的三倍。结果表明，在该地区目前的温度下，直接热应激对生殖器官的作用相对较小。CO2浓度升高对蒸腾效率的影响应在未来几十年内降低产量对EDD的敏感性，但最多可降低25%。
Statistical studies of rainfed maize yields in the United States(1) and elsewhere(2) have indicated two clear features: a strong negative yield response to accumulation of temperatures above 30 degrees C (or extreme degree days (EDD)), and a relatively weak response to seasonal rainfall. Here we show that the process-based Agricultural Production Systems Simulator (APSIM) is able to reproduce both of these relationships in the Midwestern United States and provide insight into underlying mechanisms. The predominant effects of EDD in APSIM are associated with increased vapour pressure deficit, which contributes to water stress in two ways: by increasing demand for soil water to sustain a given rate of carbon assimilation, and by reducing future supply of soil water by raising transpiration rates. APSIM computes daily water stress as the ratio of water supply to demand, and during the critical month of July this ratio is three times more responsive to 2 degrees C warming than to a 20% precipitation reduction. The results suggest a relatively minor role for direct heat stress on reproductive organs at present temperatures in this region. Effects of elevated CO2 on transpiration efficiency should reduce yield sensitivity to EDD in the coming decades, but at most by 25%.