Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia.
Sci Total Environ. 2022 Dec 1;850:157915. doi: 10.1016/j.scitotenv.2022.157915. Epub 2022 Aug 6.
Cities have been described as 'heat islands' and 'dry islands' due to hotter, drier air in urban areas, relative to the surrounding landscape. As climate change intensifies, the health of urban trees will be increasingly impacted. Here, we posed the question: Is it possible to predict urban tree species mortality using (1) species climate envelopes and (2) plant functional traits? To answer these, we tracked patterns of crown dieback and recovery for 23 common urban tree and shrub species in Sydney, Australia during the record-breaking austral 2019-2020 summer. We identified 10 heat-tolerant species including five native and five exotic species, which represent climate-resilient options for urban plantings that are likely to continue to thrive for decades. Thirteen species were considered vulnerable to adverse conditions due to their mortality, poor health leading to tree removal, and/or extensive crown dieback. Crown dieback increased with increasing precipitation of the driest month of species climate of origin, suggesting that species from dry climates may be better suited for urban forests in future climates. We effectively grouped species according to their drought strategy (i.e., tolerance versus avoidance) using a simple trait-based framework that was directly linked with species mortality. The seven most climate-vulnerable species used a drought-avoidance strategy, having low wood density and high turgor loss points along with large, thin leaves with low heat tolerance. Overall, plant functional traits were better than species climate envelopes at explaining crown dieback. Recovery after stress required two mild, wet years for most species, resulting in prolonged loss of cooling benefits as well as economic losses due to replacement of dead/damaged trees. Hotter, longer, and more frequent heatwaves will require selection of more climate-resilient species in urban forests, and our results suggest that future research should focus on plant thermal traits to improve prediction models and species selection.
城市被描述为“热岛”和“干燥岛”，因为城市地区的空气比周围的景观更热、更干燥。随着气候变化的加剧，城市树木的健康将越来越受到影响。在这里，我们提出了一个问题：是否可以使用（1）物种气候范围和（2）植物功能特征来预测城市树种的死亡率？为了回答这些问题，我们在澳大利亚悉尼跟踪了 23 种常见城市树木和灌木物种在创纪录的 2019-2020 年澳大利亚夏季树冠枯萎和恢复的模式。我们确定了 10 种耐热物种，包括 5 种本地物种和 5 种外来物种，它们是城市种植的气候适应选择，很可能在未来几十年继续茁壮成长。由于死亡率、导致树木移除的健康状况不佳以及/或广泛的树冠枯萎，13 个物种被认为容易受到不利条件的影响。树冠枯萎随着物种原籍气候最干燥月份的降水量的增加而增加，这表明来自干旱气候的物种可能更适合未来气候下的城市森林。我们使用基于简单特征的框架，根据其干旱策略（即耐受或回避）有效地对物种进行分组，该框架直接与物种死亡率相关联。七个最易受气候影响的物种采用了避旱策略，具有较低的木材密度和较高的膨压损失点，以及具有低耐热性的大而薄的叶子。总体而言，植物功能特征比物种气候范围更能解释树冠枯萎。大多数物种在经历压力后需要两个温和、湿润的年份才能恢复，这导致冷却效益长期丧失，以及由于死树/受损树木的更换而造成的经济损失。更热、更长和更频繁的热浪将需要在城市森林中选择更具气候适应能力的物种，我们的研究结果表明，未来的研究应侧重于植物热特性，以改进预测模型和物种选择。
