Infrared radiative performance of urban trees: spatial distribution and interspecific comparison among ten species in the UK by in-situ spectroscopy
Infrared radiative performance of urban trees: spatial distribution and interspecific comparison among ten species in the UK by in-situ spectroscopy
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DOI：
10.1016/j.buildenv.2020.106682
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发表时间：
2020-04
影响因子：
7.4
通讯作者：
Jie Deng;B. J. Pickles;S. Smith;Li Shao
中科院分区：
文献类型：
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作者：
Jie Deng;B. J. Pickles;S. Smith;Li Shao
了解树种与太阳辐射相互作用的方式以前主要集中在阳光的透射和反射上，通常是通过检查单个叶子。在这里，我们使用了树冠光谱测量方法进行现场测试的辐射性能的10个常见的种植树种在英国。树冠透反射率（透射和反射的综合效应）进行了检查，以确定i），如何辐射性能的个别树木在一个物种内的空间变化，和ii），如何红外辐射性能的树种之间的差异。我们的研究结果表明，树冠透反射率取决于树冠形态，局部树叶分布（叶密度，冠叶轮廓的间隙，凹或凸冠形状），太阳高度和叶片大小的组合。在空间上，最强的树冠transflection被发现主要是对天空的阳光照射的一面的树木，而不是对天顶，这意味着对周围的建筑物和行人的红外transflection是实质性的。在晴天，所有10个树种的冠层透光率与太阳高度呈线性相关。因此，选择45°的太阳高度作为比较种间差异的基准条件。种间比较表明，种间差异的红外辐射性能水平强烈依赖于叶片的大小时，没有明显的差距或凹陷形状的树冠内。我们的研究结果为理解城市树木与周围建筑环境之间的辐射相互作用以及城市热应力缓解中的树种选择提供了见解。
Understanding the ways in which tree species interact with solar radiation has previously focused on transmission and reflection of sunlight, typically by examining individual leaves. Here we used a tree crown spectroscopy measurement method to conduct in-situ tests on the radiative performance of ten commonly planted tree species in the UK. Tree crown transflectance (comprehensive effect of transmission and reflection) was examined to determine i), how radiative performance of individual trees varies spatially within a species, and ii), how infrared radiative performance differs between tree species. Our results show that tree crown transflectance depends on the combination of tree crown morphology, local foliage distribution (leaf density, gaps in crown foliage contour, concave or convex crown shapes), solar altitude and leaf size. Spatially, the strongest tree crown transflection was found primarily towards sky on the sunlit side of trees rather than towards the zenith, meaning that infrared transflection towards surrounding buildings and pedestrians is substantial. For all ten species, the tree crown transflectance in the frontal sunlit area was linearly correlated with solar altitude on sunny days. Hence, a solar altitude of 45° was chosen as the benchmark condition for comparing interspecific differences. Interspecific comparison indicated that interspecific differences in the infrared radiative performance levels were strongly dependent on leaf size when no obvious gaps or concave shapes were present within the tree crowns. Our findings provide insights for understanding radiative interactions between urban trees and surrounding built environment, as well as for tree species selection in urban heat stress mitigation.