北京地区外来入侵植物分布特征及其影响因素

为研究北京地区入侵植物扩散与分布规律,探讨影响入侵植物分布的驱动因子,对北京郊区12区县入侵植物分布情况进行了实地调查,分析了北京地区入侵植物的水平分布格局和其随海拔梯度的变化规律,并对影响入侵植物种数和分布的各类因子进行了相关分析。结果表明:北京地区共有外来入侵植物47种,不同区县入侵植物物种数量差别较大,通州、门头沟等外来入侵植物分布较多;并形成3个明显的集中分布区域。入侵植物在不同海拔高度都有分布,其数量随海拔梯度的变化规律表现出线形关系,低海拔区域100—900 m是外来入侵植物分布数量较多的海拔范围。通过对不同影响因子与入侵植物物种多度相关分析表明,进口额、一级公路密度与外来入侵植物数量显著负相关,而与林木覆盖率显著正相关,这些结论与入侵植物分布与扩散一般规律相悖,这与北京地区森林起源与以及人类活动对于植被干扰多样性和不确定性形成的景观破碎化有关,多样性干扰为更多植物入侵提供了可能性。入侵植物分布格局和多样性人为活动的干扰使其防控难度加大。

Distribution pattern and their influcing factors of invasive alien plants in Beijing

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.