Historical introduction, geographical distribution, and biological characteristics of alien plants in China

Using the published literature and records, this study investigated the historical introduction, geographical distribution, and biological characteristics of 404 alien plants in 32 provinces (including municipalities) in China. The results showed that three fifths of the alien plants was introduced for intentional purposes, and the introduction of alien plants increased with time from 139 BC to the current time, especially during historical events that played an important part in the process of introduction. The geographical distribution of alien plant species tended to decrease from the south and the east to the north and the west. Annual average precipitation (Y = 7.51X + 7.05, R-2 = 0.67) and temperature (Y = 0.07X + 41.54, R-2 = 0.67) had a linear relationship with alien plant introduction throughout China. Furthermore, population density and economic conditions also affected and promoted plant invasions in China. The life forms were well adapted to regional precipitation and temperature, but different life forms of alien plants were not consistent with the distribution tendency based on the quantity of alien plants. There was a higher percentage of annual and biennial plants in the northern provinces (e.g. 66.7 and 15.7% in Inner Mongolia), whereas there were more perennial and woody plant species in the southern provinces (e.g. 37.0 and 21.2% in Hainan). Family characteristics could not accurately predict plant invasions; however, predictions based on genera were acceptable. In addition, the origin of alien plants can also predict the distribution and potential risk of invasions. Thus, our study investigated the factors affecting plant invasions in order to provide information on the prevention and control of alien plants.