The Key Laboratory for Silviculture and Forest Conservation of Ministry of Education,,,,The Key Laboratory for Silviculture and Forest Conservation of Ministry of Education
We investigated the invasive plants in twelve districts and counties in Beijing to study the distribution patterns and their influcing factors of these invasive plants. Based on the GIS technology and the curve regression analysis, the horizontal and vertical distribution patterns of the invasive species were analyzed. The correlation analysis for the invasive species and influcing factors which include human activities and circumstance, were also carried out. The results showed that there are total 47 species of invasive plant species in Beijing. It included three types of invasives species, which include the officially announced invasive species, concerned species and controversial species. The most widely distributed species are Amaranthus retroflexus, Pharbitis hederacea, Pharbitis purpurea, Bidens pilosa, Eleusine indica, Pharbitis nil, Rhus typhina, Robinia pseudoacacia, and etc. Especially for Ambrosia artemisiifolia and Ambrosia trifida,which have posed huge threats to human health, exist in five investigated villages and towns.Moreover, there were significantly differences of amounts of these plants among twelve districts and counties. The invasive species have significantly spread much more in Tongzhou、Miyun、Mentougou、Huairou、Fangshan and Yanqing. Three dispersal centers were apparently concentrate as follows: the area near Wuling Mountain and Yunmeng Mountian in northeast of Beijing; Xiayun Mountain and Shidu of Fangshan district and Fengtai district in the midwest of Beijing; and all villages and towns of Tongzhou in southeast of Beijing. At present, the invasive plants distribute widely in different altitudes while mainly distribute at 100-900m. Especially between 401m and 500m, which accounts for 21. The numbers of the invasive species along with the altitude fit the linear function. Along with the rise of altitude, the number of the invasive species tended to decline. The number and distribution range of invasive species in high degree human activity areas are higher and wider than in those of low degree human activity areas. Similarly, the distribution areas of the most invasive species in higher degree human activity were larger than the that of in low degree human activity areas. The correlation analysis of the number of the invasive plant species and some possible influcing factors revealed that the number of the invasive alien species are negatively related to the amounts of imports and first-class highway density, while positively related to the vegetation coverage rates. These phenomena might be opposite to the normal rules of the distribution and spread of the invasive species, but they could be explained by the potential influence of the origin of the forests and landscape fragmentation which caused by human activities diversity and its uncertainty in Beijing. The diverse disturbance supply that more habitat for more plants. The distribution pattern of invasive species and the various human activities might increase the difficulty in preventing and controlling the invasive plants.