行道树对城市道路交通环境的响应研究

EFFECT OF URBAN TRAFFIC ENVIRONMENT ON ROADSIDE TREES

以南方常见的8种城市行道树作为研究对象,并以各自在远离城市道路交通环境生长的树种作为对照,对行道树及其对照样品叶片和树皮的重金属铅和镉、电导率、pH值、叶片伤斑率及叶片表皮结构气孔数等进行测定,以探讨不同树种对交通环境的响应.结果表明,与对照树种比较,行道树叶片和树皮能累积城市道路交通环境中的重金属铅和镉,其电导率和叶片的伤斑率增加,pH值下降.叶片气孔数的变化随树种不同有所差别,如阴香〔Cinnamomumbur-manii(Nees)〕等的叶片气孔数比对照少,而细叶榕(FicusmicrocarpaL.)等比对照多.根据行道树的生长状况及净化重金属的能力,8种供试植物中,白兰(MicheliaalbaDC.)和垂叶榕(FicusbenjaminaL.)最适合选作行道树,而阴香因其在交通环境中生长不良,净化效益差,不宜选作交通密集区的行道树种.

The leaf and bark samples of 8 speices of roadside trees, commonly planted in South China, were taken from two areas, that is, urban traffic polluted areas and comparatively unpolluted parks far from motor traffic. The heavy metals, lead （Pb） and cadmium （Cd） , electric conductivity and pH value in the leaves and barks of the samples, and the euticular feature as stomatal numbers of the leaves were measured to reveal the effect of urban traffic environment on roadside trees. The results indicated that the heavy metals, Pb and Cd contents, and electric conductivity in the samples of roadside trees increased, while pH value decreased, and the stomatal numbers of the leaves of roadside trees varied with the different plants compared with the control samples taken from the parks. For example, the stomatal number of Cinnamomum burrnanii （ Nees ） was smaller than that of the controls＇samples. But the stomatal number of Ficus microcarpa L. was bigger than that of the control. Based on the growth of and heavy metal purification by the 8 speices, Michelia alba DC. and Ficus benjamina L. were considered most suitable for roadside trees, but Cinnamomum burmanii （Nees） was not because it absorbed heavy metals and grew poorly. Fig 3, Tab 3, Ref 17