【摘要】 <正>我国地域广大,环境复杂,植物种类在25,000种以上,兼有寒带、温带、热带三种类型。各地区的气候、土壤、地形的差异很大,而气候、土壤、地形的不同组合和相互影响,又都根本地影响着各地区的植被群落。另一方面,我国第四纪未经完全受大陆冰川的更多还原

【Abstract】 China has a very vast area, complex environment and rich plant species comprising arctic, temperate and tropical types. In addition to climatic, edaphic and topographical differences in different geographical regions, the vegetation-ty-pes have been made more complicated by certain geological factors, the glacial factor, for instance, which resulted in remaining certain amount of preglacial remnants in certain places. The anthropic effects for more than 5,000 years have certainly caused profound changes in our natural vegetation. In general, the en-vironmental factors which affect the vegetation most are climatic, topographic, edaphic, bistbric and biotic ones among which the climate is certainly the most important, but in connection with other features its effect is expressed differently in different regions. In China, in western part, especially in Tibetan plateau, the topographical factor becomes most prominent; in northern and eastern parts the cold tide predominates, in the coastal region the Pacific and Indian monsoons play the leading part.On account of these conditions, the vegetation cover of China may be divided into 3 main types, i. e. forests, steppes or meadows, and deserts. Forests are chiefly present in the moist N. E. China, S. China and S. W. China, while the other 2 types in the dry N. W. part. The forests are again divided into 7 types, the steppes or meadows into 3, and the deserts into 2, thus constituting altoge -ther 12 types of vegetation in this country.1. The subarctic coniferous forests Such forests are present in our northmost region which is characterized by intense coldness with yet a moderate humidity, and where the soil is of a podzolic type but is often permanently frozen. The vegetation has therefore developed into cold-resistant coniferous forest of the Taiga type. In the Great Khingan, Larix Gmelini and Pinussylvestris var. mongdica are the dominant trees, while in the southern part of the Altai Pinus Cembra var. s.birica and Larix sibirica are most abundant. Betula and Populus appear in the secondary forests. Qucrcus (Q. mongdica in Great Khingan only) and other broad-leaved trees are very scanty. Sphagnum bogs and mea-dows are often found with the forest, having many plants similar to those of N.Europe and Siberia and, moreover, several arctic elements (like Empetrum).2. The cold temperate mixed forests In the eastern part of Northeast there are extensive and luxuriant mixed forests, where the climate is not so cold as the subarctic one, but is more humid and with a podzolic soil. The dominant spe-cies are Pinus koraiensis and Picea jezoensis. There are also many kinds of broad-leaved trees, as Quercus, Betula, Populus, Tilia, Acer, Ulmus, Fraxinus, and the famous tertiary relic Phellodendron. Sedge-bogs, meadows, and forest-swamps with Lafix olgensis as the dominant plants are often found in the valleys, beside the forests, luxuriant growth of shrubs and herbs with several endemic species, ter-tiary in origin, can be found. This type is one of the most important forests supplying timbers to the country.3. The temperate summer-green forests N. China is chiefly a region of con-tinental climate with a moderate rainfall, a severe winter and a long period of drought throughout winter and spring. The vegetation is naturally of a summer-green broad-leaved forest type. On account of the long continued agricultural practice the primitive aspects of vegetation can be no longer seen, except in a few inaccessible places. Trees commonly seen are the species of Quercus, Acsr, Catalpa, Ailarthus, Fraxinus, etc., intermixed with certain drought-resistant co-nifers, as Pinus tabulaeformis and Thuja arientalis. On the Peninsulas of Shan-tung and Liaotung, because of a more favourable oceanic climate, the floristic composition is richer and many southern forms are found. The outstanding plants are Pinus densiflora and Qu&rous acutissima. The condition of the loess plateau is more arid than the other places. On account of over-cutting and over-grazing, the low hills are covered by secondary更多还原