中国种子植物特有属的分布区学研究

本文讨论了分布区的概念和分布区周界的划定方法，认为邻近距离平均法(mean propinquity method)对划定分布区的周界具有较大的科学性和可用性。根据247幅中国种子植物特有属的分布区图及其属内各种在属分布区范围内的分布情况，我们将中国种子植物特有属划分为5个分布区类型。本文还对中国种子植物特有属分布区与地形和气候条件的关系，以及与植被和植物区系界线的关系进行了分析，提出制约分布区形状和大小的主要决定因素，并指出种在属分布区内的分布规律的研究对次一级植物区系分区或植被区划研究具有重要意义。

AREOGRAPHY OF THE ENDEMIC GENERA OF SEED PLANTS IN CHINA

Phytogeography is interested in the delimitation of floristic sets and in the origin of their different elements, while areography focuses its attention on the form and size of geographical range of species and other taxa. Ecology or, more precisely, ecogeography, answers questions on the reasons for the form and size of areas. From the current distribution maps of the 247 endemic genera of seed plants of China, it is possible to envisage five main models of partitioning:contiguity (A1-A2); inclusion (B1-B2); overlap (C1-C2); solitary (D1-D2) and disjunction (E1-E2). Many species appear to be limited in at least part of their geographic ranges by physical factors, such as temperature regime, water availability, and geographic and topographic accidents. For an endemic genus that has not reached a barrier, its size of area depends upon the capacity of species to adapt to different enviroments and to colonize different habitats. Speranskia with three species, for example, has a fairly extensive range in eastern China, but within its area it grows on forested slopes, in thickets, in weedy places, on roadsides, near habitations and in steppe area. The genus Notoseris with 14 species, however, has a smaller range across south central and southeastern China, but within its area its local distribution is confined strictly to the edges of forests and grassy slopes in forested areas. Above, examples show that the genera with a high number of species are not certainly more widespread than the genera with a low number of species. The conditions of topography that modify the shape of climatic regions (such as altitude, basin, proximity to large bodies of water, etc. ) also modify the shape of major areas, because climatic boundaries constitute the principal boundaries of floristic and vegetational areas. More local features of topography affect the shape of smaller areas and determine the shape of areas. In the study of generic areas, it should be clearly emphasized that it is of extreme importance to focus attention on the distributional patterns of species, which may show great significance for the regionalization of flora and vegetation.