广西大瑶山的银杉研究

STUDIES ON CATHAYA ARGYROPHYLLA OF DAYAOSHAN, GUANGXI

银杉自1955年首次在广西花坪林区发现之后,时隔30多年,而于1986年在大瑶山土县,即北纬24°9′—24°24′发现了银杉的新分布,从而把我国银杉的分布区向南推移了约1°30′,成为目前已知银杉地理分布的最南界。大瑶山的银杉不但植株高大,树干圆满通直,而且在水平、垂直分布、生境条件和所处林带等方面均与各地的分布点有明显的不同。 大瑶山银杉的上层林木以松科为主,中下层以壳斗科、樟科和山茶科占优势。按照Raunkia生活型分类系统的分类结果,常绿成分和革质叶占绝对优势(分别占98.1％和90.4％)。革质叶和细型叶常绿针叶大高位芽植物是群落的主要成分;单叶、革质、小型叶和中型叶的常绿阔叶中高位芽和小商位芽植物在中下层发育最好。根据样地内幼苗幼树少,和缺乏中下层林木的事实表明,它在群落中的稳定已受到严重的影响。在样地外和其他林地上,虽可见到少量中下层林木和幼苗幼树,但从群落的发展趋势来看,这里的银杉混交林最终要由常绿阔叶林所更替。 本文亦根据树干解析论述了银杉的生长情况。 1981—1982年大瑶山综考后,金秀瑶族自治县林业局和国营金秀林场,在进行杯区树种资源调查时,在县城东北方约15公里,地名为土县一带天然林中,首先发现了银杉(Cathaya argyro-phylla Chun et Kuang)。

It is more than 30 years since Cathaya argyrophylla was found in Hua-ping Reserve in Guangxi in 1955. The discovery of this relic species in Dayaoshan in central Guangxi, the souther border ever known for the distributional area of this species, is a new record. In Dayaoshan, the Cathaya trees is big and tall, the tallest one reaches a height of 30 m. In the forest of Cathaya argyrophylla the species of the upper layer are species of Pinaceae; while those of the middle and lower layers are species of Fagaceae, Lauraceae and Theaceae. According to Raunkiaer's classification system of lifeform, the predominent components are evergreen and coriaceous-leaved components (make up 98.1% and 90.4% respectively). Megaphanero-phyte with coriaceous and small leaves evergreen needle-leaved is the main component of the vegetation; the mesophanerophyte and nanophanerophyte with simple, coriaceous, small and middle-sized leaves develop the best. The fact of a few seedlings and lacking of saplings and middle aged trees in the sample plots shows that serious influences have been made up on the stability of the species in the community. Although there are some trees or saplings seen in the middle and lower layers of the, forest outside the sample plots and other stands, but it tends to be seen by the development of the community that the Cathaya mixed forest will be replaced at last by the evergreen broad-leaved forest. By means of stem analysis the growth of this tree is also discussed in the present paper.