广西植物地理的基本情况和基本特征

<正> 广西处于北纬20°54′—36°20′,东经104°28′—112°04′之间。全区总面积23万6千平方公里,约占全国面积的2.46％。本区西靠云贵高原,南部濒临海洋,地跨热带和亚热带。地势东南低、西北高,因而河流主要是由西北向东南流入南海。广西境内群山环绕,在群山之中往往出现一些不大的盆地,在西江干流上亦有若干局部的小平原。广西大部分地区属于古老的地块—华夏陆台,因此,在海拔高度上,除东北和西北部以及中部、东部、东南部的弧形山脉、勾漏山脉和十万大山在500米以上者外,其余地区一般在500米以下,属丘陵地。区内超过2000米的山峰有五座。岩溶地形广泛发育,散布于区内各地,形成千奇百怪的岩溶地貌,构成广西地貌的主要特征之一。

GENERAL INFORMATION AND FUNDAMENTAL FEATURES OF PLANT GEOGRAPHY OF GUANGXI

The primary vegetation in Guangxi, mainly, is arbor vegetation with most evergreen broad-leaved forests. Because the vegetation has long been destroyed over and over again, it has become typical secondary forest and grass-land. The existing forms of natural vegetation in Guangxi can be divided as: evergreen broad-leaved forest vegetation, shrub-herbaceous vegetation and herbaceous vegetation.The total number of species of the vascular plants in Guangxi are over 7,000, belonging to 1,698 genera and 183 families. with preliminary study on the zonal distribution for 1,698 genera and on the geographical distribution of the chief vegetational forms in Guangxi, the fundamental features of plant geography of Guangxi may be as follows. 1 ) The plant zonal character of Guangxi belongs to the tropical-subtropical; 2 ) In Guangxi , there are differences between the south and the north in distribution of plants, and also differences between the east and the west. The latitudinal limit of each zone of plants is low in the east and higher in the west. The biotope in the east is moister than in the west; 3 ) According to the density of plants distributed, there are four regions in the flora of Guangxi, that is, the north and northeast, the west and northwest, the southwest and the east regions; 4 ) The distribution of the limestone hills and calcareous soil account for the greatest regional differences of plants in each zone; 5 ) For comprehensive effect of the topography and of cold waves from north, the plants of the north and the south distribute crosswise in Guangxi; 6 ) Having been distroyed again and again for a long time, most types of vegetation, differ more and more, with the primary one, become xerophytic or drought-enduring; 7 ) The distribution of the long-term cultivated economic plants suggests, more or less, the identity of the geographycal conditions.