Isotope-based water-use efficiency of major greening plants in a sponge city in northern China

To tackle urban water issues, the Chinese government has promoted the construction of sponge cities in recent years. Thirty cities have been designated as experimental sites to serve as models for future sponge city construction, as more than 80% of the built-up urban areas in China must reach the standards of sponge cities by 2030. Greening plants play an important role in sponge cities, and water-use efficiency (WUE) is a vital index to determine whether plants could adapt to and grow healthily in environments with water deficits. In this study, WUE of greening plants was quantified by measuring the stable carbon isotope fractionation. Suitable plants for the green spaces in Guyuan sponge city, in northern China, were selected based on their WUE, and the main factors affecting WUE were studied in four habitats within the city. Plant species identity had the greatest effect on WUE, while habitat and plant life form had lower effect, illustrating that WUE is a relatively stable and reliable index for the classification of plant species. We can improve the WUE and ecological function of green spaces in sponge cities by using isotope technology to select suitable plant species with high WUE. To our knowledge, this study is the first to select plant species for sponge city by using this method, providing a quick and scientific method for the selection of greening plants for future sponge cities.

为应对城市水问题，中国政府近年来积极推进海绵城市（Sponge City）建设。目前已有30个城市被列为试点城市，作为未来海绵城市建设的示范样板；根据规划，到2030年，中国超过80%的城市建成区需达到海绵城市建设标准。绿化植物在海绵城市系统中发挥着关键作用，水分利用效率（Water-use Efficiency, WUE）是衡量植物能否在缺水环境中适应并健康生长的核心指标。本研究通过测定稳定碳同位素分馏，对绿化植物的水分利用效率进行了量化分析。研究以中国北方固原海绵城市的绿地为对象，基于植物的水分利用效率筛选适配的绿化植物，并针对城市内四类生境开展了水分利用效率影响因素的探究。结果显示，植物物种种类对水分利用效率的影响最为显著，而生境类型与植物生活型的影响相对较弱，这表明水分利用效率是一项用于植物物种分类的稳定且可靠的指标。通过同位素技术筛选高水分利用效率的适配植物物种，可有效提升海绵城市绿地的水分利用效率与生态功能。据我们所知，本研究首次采用该方法为海绵城市遴选适配植物物种，为未来海绵城市绿化植物的筛选提供了一种快速且科学的可行路径。