Species in humid, tropical regions frequently experience dangerously high heat. The danger of high temperatures is especially pronounced in cities due to the urban heat island effect. Trees can greatly reduce surface temperatures and mitigate the urban heat island effect through evapotranspiration and by reflecting solar radiation before it is absorbed by impervious surfaces. However, trees may also be physiologically susceptible to the effects of climate change as high temperatures exceed their physiological limits. In this study, we assessed how the urban tree community in subtropical Miami (Florida, USA) will be impacted by climate warming and how impacts will differ between native and exotic tree species. We calculated the thermal safety margin (TSM) in Miami for each of 235 tree species as the difference between the maximum temperature experienced by a species within its range and the current and future (2100) projected maximum temperature in the city. We also combined TSMs, a metric of resilience to heat, with each species’ drought, wind, and salt tolerance to identify species that are resilient to multiple relevant stressors. We found that by 2100 Miami will be too hot for 16–41 % of the tree species currently planted in the city, depending on the climate change scenario. Native tree species will be disproportionately impacted compared to exotics, likely because most exotic species originate in the tropics, whereas most species native to Miami are primarily subtropical or temperate. The species that are more resilient to multiple stressors include mostly native species, several of which are ideal shade trees. Urban greening initiatives should carefully consider tree plantings to optimize the long-term health of urban tree communities and the services that they can provide to cities in the future.

中文翻译：

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气温上升将使迈阿密的街头生活更加充满异国情调


潮湿热带地区的物种经常经历危险的高热。由于城市热岛效应，高温的危险在城市中尤为明显。树木可以通过蒸发蒸腾作用和在太阳辐射被不透水表面吸收之前反射太阳辐射，大大降低地表温度并减轻城市热岛效应。然而，树木在生理上也可能容易受到气候变化的影响，因为高温超过了其生理极限。在这项研究中，我们评估了亚热带迈阿密（美国佛罗里达州）的城市树木群落将如何受到气候变暖的影响，以及本地和外来树种之间的影响将如何不同。我们计算了迈阿密 235 种树种中每一种树种的热安全边际 （TSM），即其范围内物种所经历的最高温度与该市当前和未来 （2100） 年预测的最高温度之间的差值。我们还将 TSM（一种衡量热恢复力的指标）与每个物种的耐旱、耐风和耐盐性相结合，以确定对多种相关压力源具有恢复力的物种。我们发现，到 2100 年，迈阿密将对该市目前种植的 16-41% 的树种来说太热，具体取决于气候变化情景。与外来树种相比，本地树种将受到不成比例的影响，这可能是因为大多数外来树种起源于热带地区，而迈阿密的大多数本地物种主要是亚热带或温带物种。对多种压力源更具抵抗力的物种主要包括本地物种，其中一些是理想的遮荫树。 城市绿化倡议应仔细考虑植树，以优化城市树木群落的长期健康以及它们未来可以为城市提供的服务。