华北植物地区的北界——兼述分区的原则和方法

THE NORTH BOUNDARY OF NORTH CHINA FLORA REGION AND EXPLANATION OF THE PRINCIPLE AND METHOD OF REGIONALIZATION

华北植物区系的北界即是东亚森林植物区系与欧亚草原与荒荒植物区系的东界。本文主要是尽可能准确地划分其界线的位置和讨论有关植物区系分区的原则和方法。根据植物区系和植被有机联系的原则,植物区系成分和它们中的建群种、优势种、特征种和特有种的分布及其与环境条件的关系,这条界线被确定为如图1表示。在最东部,华北与东北植物区系界线是从开原向南到岫岩,然后向东至中、朝国界的浑江口。从开原向西南延伸2000余公里至兰州。在这条界限以此为以针茅为优势种的蒙古草原南界,其以南为以白羊草为优势种的暖温带草原并结合有东亚森林植物区系的草、灌丛。

The northern boundary of North China Flora Region is the bor der line between East Asia forest flora and Eurasia steppe-Asia desert flora. This paper is to make the border line of them and discuss on the principle and method of floristic regionalization. Based upon the principle of united origin in flora with vegetation, the flora elements and their distribution of dominant, characteristic and endemic species as well as environmental conditions, the line is shown as follows and figure 1. At the most eastern part it is the boundary between North China and Northeast China Region from Kai-yuan southward to northern Xiu-yan, and then eastward to country boundary with Korea at the river mouth of Hun Jiang in Liaoling Province. From Kai-yuan southwestward about more than 2000km to Lanzhou, it goes along the south boundary of Monglian steppe and across the transitive forest-steppe zone by the boundary between the steppe communities composed of Bothrichioa ischaemum, Themeda triandre var. japonica and of StiPa baicalins and Stipa bungeana.