北京市春季天气状况对针叶树叶面颗粒物附着密度的影响

对北京市侧柏、圆柏、油松和云杉冲洗与未冲洗植株春季1个月内叶面颗粒物附着密度进行了观测,并对照逐日气象数据和测试树种叶表面微形态,分析了天气状况对叶面颗粒物附着密度的影响。结果表明,春季降雨、大风、沙尘等天气状况交替出现导致叶面颗粒物附着密度随之变化,大多数时间低于冬季。测试树种叶面部分颗粒物附着牢固,不能被中等强度15 mm降雨冲掉。5~6级大风不会使叶面颗粒物附着密度减少。与本地扬尘相比,外来入侵沙尘可使叶面颗粒物附着密度较大增加。侧柏和圆柏叶表面密集脊状突起间的沟槽可深藏许多颗粒物,且颗粒物固着牢固,不易被降雨和大风去除。油松叶表面光滑、粘性大,易于小颗粒物的附着,但颗粒物容量较低,附着不牢固。云杉气孔周围较宽凹槽利于牢固滞留较大颗粒物,能有效捕获粒径较大的外来沙尘。

Effects of weather condition in spring on particulates density on conifers leaves in Beijing

In this paper,the particulates density on the leaves of washed-and unwashed Platycladus orientalis,Sabina chinensis,Pinus tabulaeformis and Picea koraiensis in Beijing was measured within a month of spring,and was compared day by day with the weather data and the micro-configuration of test species' leaf epidermis.The results showed that the particulates density on conifers leaves changed with the alternative appearance of rainy,windy and dusty weather in spring,and in most cases,had a lower value than in wintertime.Parts of the particulates were firmly adhered to the leaf epidermis,and could not be removed by medium intensity(15 mm) precipitation.Five or six class strong wind could not reduce the particulates density.Compared with the local dust,extraneous dust made the particulates density on leaves increased greatly.The grooves between vertebral heaves on the leaf epidermis of P.orientalis and S.chinensis could hold many small particulates deeply and firmly,making them hard to be removed by precipitation and wind.The leaf epidermis of P.tabulaeformis was smooth and sticky,and thus,had a small and easily saturated capacity of holding particulates.The particulates loosely adhered to its leaf surface were prone to be removed.The wider grooves around the stomas of P.koraiensis leaf epidermis were in favor of retaining larger size particulates,and hence,could effectively capture larger size extraneous dust.