Composition of plant species and their distribution patterns in Beijing urban ecosystem
北京城市生态系统植物种类构成及其分布特征

Plants are the important components in Beijing urban ecosystems and play an essential role in urban landscape, environmental purification, and microclimate modification. In this study, we made a systematic investigation on Beijing urban plants based on urban functional zones, including parks, residential areas, roads, school yards, gym center and institution yards, and square and public buildings within fifth ring of Beijing. The results showed that there were 536 plants species, which belonged to 307 genera and 99 families in Beijing built area. Among them, 279 species were Beijing native plants, which was accounted for 52.05% of total urban plant species; 150 species were introduced from other regions of China, 27.99% of total urban plants, and 107 species were introduced from foreign countries, 19.96% of total urban plants. The floristic analysis of Beijing urban plants suggested that the flora in Beijing built area was mainly North Temperate elements, the ratio of North Temperate elements was 21.05%, and much lower than 30.30% in Beijing suburb. The plant ratios of Temperate Asia elements, Old World Tropic elements, Cosmopolitan elements were lower than those in Beijing suburb as wells. While, the plant ratio of Tropical elements was increased slightly. The specie richness distribution varied in different urban functional zones. The plant species richness was highest in parks then in schoolyards, and it was lowest the in square and public building. There were more than 50% of urban plants could be found in parks and schoolyards, which was a species pool in Beijing built area. The ratios of native plants were quite low in all sampled functional zones, and even in park and schoolyards, the native plant ratios were only 53.86% and 52.52% respectively. The parks had the highest species diversity of arbor and shrub, but the underdeveloped area had the highest species diversity of herbs. It may implied that the urban undeveloped areas be considered as good potential herbage species pool for urban, and extensive management of green spaces be a main cause for the low plant species diversity in urban built area. Native species protection shouldn't be neglected during city development.