The impact of expanding flooded land area on the annual evaporation of rice
The impact of expanding flooded land area on the annual evaporation of rice
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DOI：
10.1016/j.agrformet.2016.04.001
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发表时间：
2016-06-15
影响因子：
6.2
通讯作者：
Detto, Matteo
中科院分区：
文献类型：
--
作者：
Baldocchi, Dennis;Knox, Sara;Detto, Matteo
尽管大米是主要的食物来源，但关于大米年蒸发量的已发表数据仍然极为有限。我们报告了六年的水稻蒸发量测量，基于涡动相关法。这种水稻是在加利福尼亚炎热干燥的气候中种植的，那里的水是稀缺而珍贵的资源。在第一年，我们发现水稻蒸发量超过潜在蒸发量，总和为1155 mm y（-1）。在接下来的几年里，我们发现年蒸发量逐年减少，到第六年减少了15%（至982毫米y(-1)）。本文的其余部分探讨了年蒸发量出现这种意想不到的减少趋势的方式和原因。我们使用能量平衡闭合和共光谱分析检查了与蒸发和通量测量中潜在偏差相关的生物物理变量（净辐射、温度、叶面积指数）的变化趋势。没有一个生物物理变量的变化足以解释这一观察结果。真正改变的是水稻的面积和附近被淹没的湿地。第一年，被淹稻田面积不足1 km(2)，相对孤立。这种情况促进了“绿洲效应”，使温暖干燥的空气从行星边界层的顶部被夹带进来；这一论点得到了共谱分析和地表能量平衡-行星边界层耦合模式分析的支持。到项目实施的第六年，被淹没的稻田和湿地面积接近6平方公里，这一水平尺度似乎抑制了“绿洲效应”。我们得出的结论是，湿地恢复项目在面积上的用水量将取决于这些项目的空间范围。(C) 2016 Elsevier B.V.版权所有
The amount of published data on annual evaporation on rice remains extremely limited despite the role of rice as a key food source. We report on six years of rice evaporation measurements, based on the eddy covariance method. This rice was cultivated in the hot dry climate of California, where water is a scarce and precious resource. During the first year, we found that rice evaporation exceeded potential evaporation rates and summed to 1155 mm y(-1). In following years, we found that annual evaporation decreased yearly, yielding a 15% reduction (to 982 mm y(-1)) by the sixth year. The remainder of the paper examined the how and why of this unexpected decreasing trend in annual evaporation occurred.We inspected trends in variations in biophysical variables (net radiation, temperature, leaf area index) associated with evaporation and potential biases in the flux measurements using energy balance closure and co-spectral analysis. None of the biophysical variables varied enough to explain this observation. What did change was the area of rice, and nearby flooded wetlands. During the first year, the flooded rice field was less than 1 km(2) in area and was relatively isolated. This situation promoted an 'oasis effect' that enabled warm dry air to be entrained from across the top of the planetary boundary layer; this contention was supported by the co-spectral analysis and analysis with a coupled surface energy balance-planetary boundary layer model. By the sixth year of this project, the area of flooded rice and wetlands approached 6 km2, a horizontal scale that seemed to inhibit the 'oasis effect'. We conclude that the amount of water used, on an area basis, by wetland restoration projects will depend upon the spatial extent of these projects. (C) 2016 Elsevier B.V. All rights reserved.