在北京东灵山暖温带森林生态系统中,选择常见灌丛土庄绣线菊(Spiraea pubescens),建立UV-B控制实验。连续3个生长季每天增补9.4 kJ·m^-2的辐射剂量,模拟臭氧衰减17%时近地表面UV-B辐射的增强。该实验的目的是在野外环境下观测,长时间人工增强UV-B辐射对土庄绣线菊叶片的气孔导度、碳同位素比率(δ¹³C)、叶含水量、叶面积、特别是水分利用效率(WUE)和叶片全氮含量等指标的影响。实验结果表明,增强UV-B辐射显著减少了土庄绣线菊的叶面积(50.1%),提高了叶片全氮含量(102%)。同时,UV-B辐射还在一定程度上(尽管统计显示不显著)降低了气孔导度(16.1%)、胞间CO₂浓度与大气CO₂浓度之比(C_i/C_a) (4.0%)、提高了碳同位素比率(δ¹³C)(20.5‰)、叶含水量(3.1%)及比叶重(SLW)(5.2%),从而导致WUE的增加(4.1%)和植物的抗旱能力增强。值得注意的是,深层土壤(30~40 cm)含水量变化会影响气孔导度、δ¹³C和WUE对紫外辐射的响应程度:在土壤干旱的季节(6月和9月),气孔导度、δ¹³C、WUE这些指标处理和对照的差异很小,但是当土壤水分充足时(7月和8月),处理和对照的差异就较为显著。另外,随着实验处理时间的延长,UV-B的效应变得不显著。相关分析表明,UV-B辐射降低了土壤含水量(30~40 cm)与土庄绣线菊叶含水量、δ¹³C、C_i/C_a和气孔导度的相关系数,增强了WUE与土壤含水量的相关性,这也许是由于UV-B辐射增强了WUE对土壤水分变化的敏感性。该研究的结果表明UV-B辐射对土庄绣线菊的形态和生长有显著的影响,但对主要水分生理指标影响不显著。

Spiraea pubescens, a common shrub in the warm-temperate deciduous forest zone, is distributed in the Dongling Mountain area of Beijing, was exposed to ambient and enhanced ultraviolet-B (UV-B, 280-320 nm) radiation by artificially supplying a daily dose of 9.4 kJ·m^-2 for three growing seasons, a level that simulated a 17% depletion in stratospheric ozone. The objective of this study was to explore the effects of long-term UV-B enhancement on stomatal conductance, leaf tissue δ¹³C, leaf water content, and leaf area. Particular attention was paid to the effects of UV-B radiation on water use efficiency (WUE) and leaf total nitrogen content. Enhanced UV-B radiation significantly reduced leaf area (50.1%) but increased leaf total nitrogen content (102%). These changes were associated with a decrease in stomatal conductance (16.1%) and intercellular CO₂ concentration/air CO₂ concentration (C_i/C_a) (4.0%), and an increase in leaf tissue δ¹³C (20.5‰), leaf water content (3.1%), specific leaf weight (SLW) (5.2%), and WUE (4.1%). The effects of UV-B on the plant were greatly affected by the water content of the deep soil (30-40 cm). During the dry season, differences in the stomatal conductance, δ¹³C, and WUE between the control and UV-B treated shrubs were very small, whereas differences became much greater when soil water stress disappeared. Furthermore, the effects of UV-B became much less significant as the treatment period progressed over the three growing seasons. Correlation analysis showed that enhanced UV-B radiation decreased the strength of the correlation between soil water content and leaf water content, δ¹³C, C_i/C_a, stomatal conductance, with the exception of WUE that had a significant correlation coefficient with soil water content. These results suggest that WUE would become more sensitive to soil water variation due to UV-B radiation. Based on this experiment, it was found that enhanced UV-B radiation had much more significant effects on morphological traits and growth of S. pubescens than hydro-physiological characteristics.