Abstract: In this paper,the vertical structure for naturally rejuvenating Leymus chinensis population after cultivated grassland and its distribution characteristic of illuminance are rcported under its different density conditions.It show that aerial biomass and leaf area at middle part of population are the highest,and they reduce gradually with upturning or downing of position.A comparison has been made between three densities,aerial biomass,leaf area index,plant height,stem height and leaf water content of L.chinensis increase with raising density of population,specific leaf weight and number of green leaves decrease with raising density.The leaf blade of L.chinensis are a erect type,more than all the angles of obliquity of superior leaves are the graeater.There are the distribution of uppermost expanded leaf at every levels from 10cm above ground surface to top of community,and possessing proportion increases gradually with raising height.These characteristics advantage the photosynthetic production of L.chinensis population.The light intensity of L.chinensis population decreases with lowering height,but the decay rate at midd1e part is the greater,and at upper and lower part are smaller.The decay rate increases with rising population density.This is closely related to the distribution of leaf area of population.

Key words: Leymus chinensis, Population structure, Density, Illuminance distribution

摘要： 本文报道了耕翻后自然更新的羊草种群在不同密度条件下垂直结构及其光照分布特征。结果表明,地上生物量和叶面积指数均以种群中部最大,向上或向下皆逐渐减小。在三种密度中,生物量、叶面积指数、株高、茎高和叶片含水量均随着密度的增大而升高。比叶重和单株绿叶数则随着密度增加而降低。羊草为直立型叶片,尤以上位叶倾角为大,其功能叶片(最上完全展开叶)从距地面10cm处向上,各层均有分布,并随着高度的上升,所占比例逐渐增大。该特征有利于羊草种群的光合生产。羊草种群内部的光照强度随着高度的降低而减弱,但中部的衰减速率较大,上部和下部较小,且随着种群密度的增大而增高。这与种群的叶面积分布特征密切相关。

关键词: 羊草, 种群结构, 密度, 光照分布