Water availability drives urban tree growth responses to herbivory and warming

1. Urban forests provide important ecosystem services to city residents, including pollution removal and carbon storage. Climate change and urbanization pose multiple threats to these services. However, how these threats combine to affect urban trees, and thus how to mitigate their effects, remains largely untested because multi-factorial experiments on mature trees are impractical. 2. We used a unique urban warming experiment paired with a laboratory chamber experiment to determine how three of the most potentially damaging factors associated with global change for urban and rural trees—warming, drought, and insect herbivory—affect growth of Quercus phellos (willow oak), the most commonly-planted large shade tree in the southeastern US, which is known for its resilience to these potential stressors. 3. In a previous study, we found that the urban heat island effect was associated with reduced growth of Q. phellos and higher abundance of Parthenolecanium scale insects, key pests of oa...1. 城市森林可为城市居民提供诸多重要的生态系统服务（ecosystem services），涵盖污染物去除与碳封存。气候变化与城市化进程正对这些服务构成多重威胁。然而，由于成熟林木的多因素实验难以开展，此类威胁如何联合作用于城市树木，以及如何缓解其影响，在很大程度上仍未得到验证。2. 本研究依托独特的城市增温实验与实验室受控箱实验组合，探究全球变化背景下对城乡树木危害最突出的三大因素——增温、干旱与昆虫植食——对柳叶栎（Quercus phellos，别名willow oak）生长的影响。柳叶栎是美国东南部种植最为广泛的大型遮荫树种，以对各类潜在胁迫的耐受性著称。3. 在前期研究中，我们发现城市热岛效应（urban heat island effect）与柳叶栎生长减缓以及软蜡蚧属（Parthenolecanium）介壳虫种群丰度升高存在关联，这类介壳虫是栎树的关键害虫，但研究内容暂未完整展示。