Urban areas face multiple environmental challenges that interact with climate change, including the urban heat island (UHI) effect. Plants can be a nature-based solution for UHI-effect mitigation, alongside various artificial materials, but their performance is only commonly compared to concrete or asphalt. Given shade's ubiquity in the urban environment, it also has a strong potential to interact with and change urban spaces' thermal performances but is rarely included in plant UHI effect-mitigation analyses. We completed an experiment to record the UHI effect-mitigation potential of 10 plant species (turf grasses, shrubs and climber/creeper plants) and eight materials (including three with high albedo) with and without shade on a rooftop in tropical Singapore across multiple sunny days in May and June 2018. We explained the infrared thermography-recorded surface temperatures of plants and materials with a surface type–time interaction in a linear regression model. Our model predicted that, without shade, except for concrete coated with white paint or infrared-reflecting white paint, plants' exterior surfaces were cooler than all artificial materials by at least ∼11 °C at 13:30 (the peak surface temperature of artificial materials). Unshaded plant species had comparable surface temperatures to shaded artificial materials and were marginally cooler than unshaded high-albedo materials. Shading caused no significant reduction of temperatures for nine of the 10 plant species studied. Our results suggest that high-albedo materials and plants can mitigate the UHI effect, either on the ground or as sources of shade to offset heat gain, and that planting up shaded surfaces would generate marginal additional cooling. Our findings should be integrated into broader trade-off analyses on the economic and health value of replacing unshaded artificial materials with plants, as UHI-effect mitigation is one of many ecosystem services provided by plants.

城市地区面临与气候变化相互作用的多种环境挑战，包括城市热岛效应。除了各种人造材料外，植物还可以是基于自然的UHI缓解方案，但其性能通常仅与混凝土或沥青相比。鉴于阴影在城市环境中无处不在，它也具有与城市空间相互作用并改变城市空间热性能的强大潜力，但很少用于植物UHI效应缓解分析中。我们完成了一项实验，记录了热带热带新加坡屋顶上10种植物（草皮草，灌木和攀援植物/爬山虎植物）和8种材料（包括高反照率的材料）的UHI缓解潜力，该热带气候在多个晴天2018年5月和6月的天数。我们在线性回归模型中用表面类型-时间相互作用说明了红外热像仪记录的植物和材料的表面温度。我们的模型预测，在没有阴影的情况下，除了涂有白色涂料或能反射红外线的白色涂料的混凝土外，植物的外表面在13:30时比所有人造材料的温度要低至少11°C（人造材料的最高表面温度）。材料）。未遮挡的植物物种的表面温度与遮荫的人造材料相当，并且略微低于未遮挡的高反照率材料。在研究的10种植物中，有9种没有遮荫导致温度没有明显降低。我们的结果表明，高反照率的材料和植物可以缓解UHI效应，无论是在地面上还是作为遮荫源以抵消热量增加，并且种植阴影表面会产生少量的额外冷却。我们的发现应纳入关于用植物替代未遮盖的人造材料的经济和健康价值的更广泛的权衡分析中，因为超高HIH效应缓解是植物提供的许多生态系统服务之一。