Nonrainfall water origins and formation mechanisms.
Nonrainfall water origins and formation mechanisms.
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DOI：
10.1126/sciadv.1603131
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发表时间：
2017-03
期刊：
影响因子：
13.6
通讯作者：
Seely MK
中科院分区：
文献类型：
--
作者：
Kaseke KF;Wang L;Seely MK
纳米布沙漠中的雾和露有多种来源，可以使用稳定同位素区分它们的形成。旱地生态系统占地球陆地总表面积的40%，广义上定义为降水量大大低于潜在蒸散量的区域。非降雨沃茨（例如雾和露）是水文循环中研究最少、特征最少的组成部分，尽管它们为旱地生态系统提供了临界水量。对于大多数系统来说，非降雨沃茨的来源在很大程度上是未知的。此外，由于技术上的限制，大多数实地研究和模拟研究往往将所有非降雨输入视为单一类别，这妨碍了对旱地对未来变暖条件的反应作出预测。本研究使用多种稳定同位素（2H，18 O和17 O）表明，雾和露有多个来源，在旱地的地下水可以通过蒸散再循环和重新分配到上层土壤剖面作为非降雨水。令人惊讶的是，非海洋衍生的（本地生成的）雾占总雾事件的一半以上，这表明在纳米布沙漠的雾区，对流为主的雾可能会转变为辐射为主的雾。这一转变将对这个依赖雾的系统中的植物群和动物群的分布产生影响。我们还表明，雾和露可以区分的基础上，占主导地位的分馏（平衡和动力学）过程中使用的17O-18O关系的形成。我们的研究结果是非常重要的全球气候变化的时代，非降雨水的重要性增加，因为降雨量预计在许多旱地生态系统下降。
Fog and dew in the Namib Desert have multiple origins and their formation can be differentiated using stable isotopes. Dryland ecosystems cover 40% of the total land surface on Earth and are defined broadly as zones where precipitation is considerably less than the potential evapotranspiration. Nonrainfall waters (for example, fog and dew) are the least-studied and least-characterized components of the hydrological cycle, although they supply critical amounts of water for dryland ecosystems. The sources of nonrainfall waters are largely unknown for most systems. In addition, most field and modeling studies tend to consider all nonrainfall inputs as a single category because of technical constraints, which hinders prediction of dryland responses to future warming conditions. This study uses multiple stable isotopes (2H, 18O, and 17O) to show that fog and dew have multiple origins and that groundwater in drylands can be recycled via evapotranspiration and redistributed to the upper soil profile as nonrainfall water. Surprisingly, the non–ocean-derived (locally generated) fog accounts for more than half of the total fog events, suggesting a potential shift from advection-dominated fog to radiation-dominated fog in the fog zone of the Namib Desert. This shift will have implications on the flora and fauna distribution in this fog-dependent system. We also demonstrate that fog and dew can be differentiated on the basis of the dominant fractionation (equilibrium and kinetic) processes during their formation using the 17O-18O relationship. Our results are of great significance in an era of global climate change where the importance of nonrainfall water increases because rainfall is predicted to decline in many dryland ecosystems.