荒漠灌木与城市绿化灌木功能性状及其对夏季热浪响应机理的差异

为比较干旱荒漠区城市绿化灌木和荒漠乡土灌木在夏季热浪期的受损差异和其对高温和热浪冲击响应机理的不同,在新疆北疆2022年夏季热浪期末期,测定了9种荒漠乡土灌木和8种城市绿化灌木的4种水分相关功能性状(水力、叶片、光合和碳经济性状),同时调查植株受损程度。调查结果表明,荒漠乡土灌木接近74%的个体在夏季热浪中未受损伤,但有56%的城市绿化灌木个体受损;水力和叶片性状方面,荒漠灌木的枝叶水势、干物质含量和导管直径的平均值低于城市绿化植物,而枝比导率、准稳态导水率、胡伯尔值、比叶面积、导管密度呈相反态势。在碳经济和光合性状方面,荒漠乡土灌木的可溶性碳含量和水分利用效率高于城市绿化灌木(P<0.05),但气孔导度成相反模式(P <0.05),而淀粉和结构性碳含量、蒸腾速率无显著差异(P>0.05);荒漠乡土灌木的性状整合度(G=0.39)高于城市绿化植物(G=0.20),且前者的关键节点个数,以及其与其他性状显著关联的个数均高于后者。结果表明,2022年夏季热浪引起荒漠乡土灌木的受损程度低于城市绿化灌木;荒漠植物在水力性状和性状整合方面存在优势,其水分吸收、运输和减少蒸腾失水的能力要强于城市绿化灌木,热浪影响下更易存活;相对城市绿化灌木,荒漠灌木可以协调功能性状间的关系,采取更多样化的适应机理将降低夏季热浪的负面影响。本研究可为干旱地区城市绿化灌木筛选以及区域生态保护政策制定提供科学参考。

Differences in functional traits and the response mechanism to summer heat wave between desert native shrubs and urban greening shrubs

In order to compare the differences in functional traits and the response mechanism to summer heat wave between desert native shrubs and urban greening shrubs, four water-related functional traits (hydraulic, leaf, photosynthetic, and carbon economic traits) of 9 desert native shrubs and 8 urban native shrubs were measured, and the damage degree of plants was investigated at the end of summer heat wave in northern Xinjiang in 2022. The results showed that nearly 74% of desert native shrubs were not damaged during the summer heat wave, whereas 56% of urban greening shrubs were damaged. In terms of hydraulic and leaf traits, the mean values of water potential, leaf dry matter content, and xylem vessel diameter of desert shrubs were lower than those of urban greening shrubs, while the twig specific hydraulic conductivity, the quasi-steady water conductivity, Huber value, specific leaf area, and xylem vessel density showed opposite patterns. With regarding to carbon economy and photosynthetic traits, the soluble carbon content and water use efficiency of desert native shrubs were higher than those of urban green shrub (P<0.05), the stomatal conductance showed an opposite pattern (P<0.05), but there were no significant differences in transpiration rate, starch and non-structural carbon content and transpiration rate (P>0.05). The traits integration of desert native shrubs (G=0.39) was higher than that of urban greening shrubs (G=0.20). The numbers of key nodes and their associated trait pairs in the desert native shrubs were higher than urban greening shrubs. The results suggested that the drought-induced damages of desert native shrubs caused by summer heat wave in 2022 were lower than those of urban green shrubs. The reason is that desert plants have stronger ability of water absorption, transport, and reducing transpiration loss than urban greening shrubs because of their advantages in water-related functional traits and trait integration. At the same time, compared with urban greening shrubs, the desert shrubs can coordinate the relationship among functional traits and adopt more diversified mechanisms to reduce the negative effects of summer heat wave. Our study provides scientific reference for the selection of urban greening shrubs and the formulation of regional ecological protection policies in arid regions.