Vertical air temperature gradients under the shade of two contrasting urban tree species during different types of summer days.
Vertical air temperature gradients under the shade of two contrasting urban tree species during different types of summer days.
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DOI：
10.1016/j.scitotenv.2018.03.168
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发表时间：
2018-08
期刊：
影响因子：
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通讯作者：
Mohammad A. Rahman;A. Moser;Anna Gold;T. Rötzer;S. Pauleit
中科院分区：
文献类型：
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作者：
Mohammad A. Rahman;A. Moser;Anna Gold;T. Rötzer;S. Pauleit
通过城市树木的树冠调节热能平衡是众所周知的。然而，关于异质城市环境及其对树冠下垂直气温梯度的影响的更多功能和量化的观点在很大程度上是缺失的。在整个2016年夏季，我们连续测量了德国慕尼黑两种常见但在生态生理和形态方面截然不同的行道树树种的树冠下三个不同高度(离地面1.5米、3米和4.5米)的气温：刺梨。(环多孔)和心叶丁香(Tilia cordata Mill.)(漫反射多孔性)。除了气温和地表温度，我们还测量了气象和土壤变量，并将夏季分为凉爽、温和、夏季和炎热四个阶段。全球辐射、水汽压差和土壤温度随着天气变暖而增加，而降水量、土壤湿度和风速则相反。总体而言，叶面积指数和树干面积较大的红豆杉提供的蒸腾作用是红豆杉的三倍。假相思。从外到内的平均气温梯度从1.8摄氏度下降到1.3摄氏度。相关数据从1.5摄氏度到仅0.5摄氏度。天气变暖了。从树冠到近地面(1.5米)，空气冷却效应的垂直衰减约为1°C。较低的土壤湿度和较高的土壤温度表明，来自冠层的冷空气与冠层下较高的感热通量经常混合在一起。相关数据与他们进行了比较。天气变暖了。这项研究指出，在极端炎热的日子里，草地表面的蒸散冷却不会那么有效，表现得像建筑表面一样，而树木树冠上相当深的阴影将是重要的。
Moderation of thermal energy balance through the canopies of urban trees is well known. However, a more functional and quantitative view of the heterogeneous urban environment and their influence on the below-canopy vertical air temperature gradients is largely missing. Throughout the summer 2016 we continuously measured air temperature at three different heights (at 1.5, 3 and 4.5 m from the ground) under the canopies of two common but contrasting street tree species in respect of eco-physiology and morphology in Munich, Germany:Robinia pseudoacaciaL. (ring porous) andTilia cordataMill. (diffuse porous). Along with air and surface temperature we also measured meteorological and edaphic variables and categorized summer time as cool, mild, summer and hot days. Global radiation, vapour pressure deficit and soil temperature increased as the days got warmer but precipitation, soil moisture and wind speed showed the reversed pattern. Overall,T. cordatatrees with higher leaf area index and sap-wood area provided three times more transpiration thanR. pseudoacacia. On an average air temperature gradient of outside to inside canopy dropped from 1.8 °C to 1.3 °C forT. cordatabut from 1.5 °C to only 0.5 °C forR. pseudoacaciaas the days got warmer. Vertical decline of air cooling effect was around 1 °C from canopy to the near-ground (1.5 m). Lower soil moisture but higher soil temperature suggested that cool air from the canopy mixed with a higher amount of sensible heat flux under the canopies ofT. cordatacompared to theR. pseudoacaciaas the days got warmer. The study indicated a threshold for extreme hot days when grass surface evapotranspirational cooling will not be as effective and act like built surfaces rather deep shading from tree canopies will be important.