The effect of shrub canopy upon surface temperatures and evaporation in the Negev Desert
The effect of shrub canopy upon surface temperatures and evaporation in the Negev Desert
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DOI：
10.1002/esp.1706
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发表时间：
2009-01
影响因子：
3.3
通讯作者：
G. Kidron
中科院分区：
文献类型：
--
作者：
G. Kidron
虽然被称为“肥沃岛”或“资源岛”，但关于灌木对沙漠小气候影响的信息很少。本文报告了1993 - 1994年和1994 - 1995年和1996-1997年生长季节（11月- 3月）在内盖夫沙漠西部尼扎纳研究地点对一对灌木及其周围进行的蒸发和温度测量。利用微型大气压计（直径10厘米，高10厘米）每月在暴露地点和灌木下方及周围（东部、南部、西部和北部）测量蒸发量，而在灌木冠层下、北部和暴露栖息地测量温度。蒸发量随蒸发量的增加顺序为：暴露>南向>西向≈东向>北向>冠下。除北部外，冠下生境的蒸发速率明显低于其他生境。在冬季，冠下生境和暴露生境之间的差异更大（冠下生境的蒸发速率是暴露生境的0.53倍），尽管夏季两种生境的温度差异更大（夏季高达14.4°C，而冬季仅为6.9°C）。结果可以用暴雨后冠下栖息地地表湿度的扩大来解释。虽然暴露的栖息地已经干燥，但冠下栖息地的表面湿度持续了几天，导致在一次暴雨之后，蒸汽压为2.15 - 2.39 kPa，而暴露的栖息地只有0.82 - 0.83 kPa。因此，具有显著低蒸发率特征的冠下生境可能在为茂密的冠下年生长提供有利条件方面发挥关键作用。版权所有©2008 John Wiley and Sons, Ltd。
Although known as ‘islands of fertility’ or ‘resource islands’, information regarding the effect of shrubs upon microclimate in deserts is scarce. Here we report on measurements of evaporation and temperatures that were carried out in and around a pair of shrubs at the Nizzana research site in the western Negev Desert during 1993–94 and during the growing season (November–March) of 1994–95 and 1996–1997. Whereas evaporation was measured monthly using mini‐atmometers (10 cm diameter and 10 cm tall) at an exposed site and under and around the shrub (at the eastern, southern, western and northern aspects), temperature was measured under a shrub canopy, at its northern aspect, and at an exposed habitat. Evaporation was aspect dependent with increasing rates in the following order: exposed > south‐facing > west‐facing ≈ east‐facing > north‐facing > under canopy. Except from the northern aspect, the under‐canopy habitat showed substantially lower rates of evaporation in comparison with all other habitats. The differences between the under‐canopy and the exposed habitat were larger during wintertime (with the under‐canopy habitat having 0·53 times the evaporation rate than that of the exposed habitat) although higher differences in temperatures characterized both habitats in summertime (up to 14·4 °C in summer as compared with 6·9 °C only in winter). The results were explained by extended surface wetness that characterized the under‐canopy habitat following rainstorms. While already being dried out at the exposed habitat, surface wetness at the under canopy habitat persisted for several days afterwards, resulting, following one rainstorm, in vapour pressure of 2·15–2·39 kPa in comparison with only 0·82–0·83 kPa of the exposed habitat. The substantially lower evaporation rates that characterize the under‐canopy habitat may thus play a pivotal role in providing preferential conditions for lush under‐canopy annual growth. Copyright © 2008 John Wiley and Sons, Ltd.