Impact of trees on the urban microclimate under climate change: Mechanisms and ecosys-tem services of urban tree species in temperate, Mediterranean and arid major cities

城市绿色基础设施，特别是城市树木及其提供的生态系统服务(如蒸腾冷却、碳储存、遮阳)是使城市适应持续气候变化的重要现代工具。尽管对适应气候的城市绿化的需求很大，但在不同的气候带，不同的城市树种对气候变化的反应在很大程度上是未知的。此外，城市气候，例如较高的温度和变化的辐射量，以及城市树木的场地条件，如有限的水可获得性、养分缺乏或有限的生根空间，可能会根据气候带和城市环境(街道与公共广场和公园)而对树木的生长、树木活力和所提供的生态系统服务产生不同的影响。为了量化树木对不同气候区城市小气候的益处，将在温带气候(德国)、地中海气候(以色列和巴勒斯坦)和干旱气候(以色列和约旦)的四个国家研究城市树木生长和生态系统服务。反之亦然，将分析不同城市环境的林分气候对树木生长和活力的影响。将沿着涵盖所有国家和气候区域的样带进行测量，以研究德国、以色列、巴勒斯坦和约旦六个选定城市的生长模式和形态特征。此外，还将建立永久性的树木实验室，在那里将以高时间和空间分辨率测量气候变量、树木生长、蒸腾以及由此产生的降温。在这些测量的基础上，可以对城市树木的生长和生态系统服务进行建模，并可以通过合并实地数据收集和建模来分析当前和未来气候情景的影响。因此，将产生关于城市树木的功能及其在不同气候带为当前和未来气候条件提供的生态系统服务的新知识。在这一新颖的联合项目中，将加强德国、以色列、巴勒斯坦和约旦的科学家与学生之间的知识共享(例如，通过培训巴勒斯坦和约旦的年轻早期研究人员)，将不同国家和气候地区的人们聚集在一起，为未来的城市绿色规划找到适当的解决方案，造福社会。该项目将在管理绿色基础设施以使城市适应气候变化方面产生新的合作和知识。

Urban green infrastructure, in particular urban trees, and their provided ecosystem services (e.g. transpirational cooling, carbon storage, shading) are important and modern tools to adapt cities to ongoing climate change. Despite the demand for climate-adapted urban green, it is largely unknown how different urban tree species react to climate change in different climate zones. Moreover, the urban climate with e.g. a higher temperature and changed radiation amounts as well as the urban site conditions for trees such as limited water availability, nutrient deficiency or limited rooting space may affect tree growth, tree vitality and the provided ecosystem services differently depending on climate zone and urban setting (street vs. public squares and parks). To quantify the benefits of trees for the urban microclimate in different climate zones, urban tree growth and ecosystem services will be studied in four countries with temperate climate (Germany), Mediterranean climate (Israel and Palestine) and arid climate (Israel and Jordan). Vice versa, the effects of the stand climate of various urban settings on tree growth and vitality will be analysed. Measurements will be conducted along a transect covering all countries and climate zones for studying growth patterns and morphological characteristics in six selected cities of Germany, Israel, Palestine and Jordan. Further on, permanent tree labs will be established, where climate variables, tree growth, transpiration and hence cooling in a high temporal and spatial resolution will be measured. On the basis of these measurements, growth and ecosystem services of urban trees can be modelled, and impacts of current and future climate scenarios can be analyzed by merging field data collection and modelling. Thus, new knowledge on the functioning of urban trees and the ecosystem services they provide in different climate zones for current and future climate conditions will be generated. In this novel joint project knowledge sharing between scientists and students of Germany, Israel, Palestine and Jordan will be increased (e.g. by training of young early stage researchers from Palestine and Jordan), people of different countries and climate zones will be brought together to find suitable solutions for future urban green planning benefitting for the wellbeing of the society. The project will result in new collaborations and knowledge for managing green infrastructure to adapt cities to climate change.