Science2014-06-10 4:19 PM

美国中西部的玉米产量增加伴随对干旱的敏感性 Greater Sensitivity to Drought Accompanies Maize Yield Increase in the U.S. Midwest

论文摘要 

据David Lobell及其同事的一项新的研究披露,在1995至2012年间,美国中西部玉米带的玉米产量一直在增加,但该作物对干旱的敏感性似乎也在增加。

实际上,在过去的18年中,玉米对干旱的敏感性一直在稳定地增加,因为这些植物已经被培育成能在更高种植密度中生长的作物。然而,研究人员注意到,密集种植的玉米似乎令人意外地对缺水更为敏感。这一趋势的一个关键性的驱动力似乎是水气压亏值(VPD),这是对空气干燥性的一种测量指标。

玉米产量会在VPD处于高水平时下降,而高水平VPD与干旱有关。如果对该地区未来干旱情况的气候预测是正确的,VPD水平的发展趋势将会在未来的50年中使玉米产量降低约15%,而如果该作物变得对干旱日益敏感,其产量的下降或可达30%。

在一则相关的《观点栏目》文章中,Donald Ort 和 Stephen Long指出了这一发现对美国未来农业的影响;美国农业目前支持全球玉米出口量的一半。

Abstract 

A key question for climate change adaptation is whether existing cropping systems can become less sensitive to climate variations. We use a field-level data set on maize and soybean yields in the central United States for 1995 through 2012 to examine changes in drought sensitivity. Although yields have increased in absolute value under all levels of stress for both crops, the sensitivity of maize yields to drought stress associated with high vapor pressure deficits has increased. The greater sensitivity has occurred despite cultivar improvements and increased carbon dioxide and reflects the agronomic trend toward higher sowing densities. The results suggest that agronomic changes tend to translate improved drought tolerance of plants to higher average yields but not to decreasing drought sensitivity of yields at the field scale.

Predicting Responses to Drought

The U.S. Corn Belt accounts for a sizeable portion of the world's maize growth. Various influences have increased yields over the years. Lobell et al. (p. 516; see the Perspective by Ort and Long) now show that sensitivity to drought has been increasing as well. It seems that as plants have been bred for increased yield under ideal conditions, the plants become more sensitive to non-ideal conditions. A key factor may be the planting density. Although today's maize varieties are more robust to crowding and the farmer can get more plants in per field, this same crowding takes a toll when water resources are limited.

Editor's Summary

Predicting Responses to Drought

The U.S. Corn Belt accounts for a sizeable portion of the world's maize growth. Various influences have increased yields over the years. Lobell et al. (p. 516; see the Perspective by Ort and Long) now show that sensitivity to drought has been increasing as well. It seems that as plants have been bred for increased yield under ideal conditions, the plants become more sensitive to non-ideal conditions. A key factor may be the planting density. Although today's maize varieties are more robust to crowding and the farmer can get more plants in per field, this same crowding takes a toll when water resources are limited.

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