Evaluation of invasibility of Wenzhou by alien plants at the scale of township

Alien plant invasion has become one of the most devascating disturbances threatening economy, environment, resources, human health, food safety, and energy. Natural factors (e.g., climate, vegetation, geomorphology) and social conditions (e.g. tourism, transportation, human population, industrial output) make the problem of alien plant invasion more complicated in number, frequency and the expansion trend. Wenzhou is a coastal region in Zhejiang Province with fast economic growth and diversified transportation of sea, land and air, where fifty nine alien plants have been found. In this paper GIS, principal component analysis and Information Entropy were used to evaluate the risk of invasibility by alien plants at the level of township. The results indicate that all 279 townships in Wenzhou could be classified into four plant invasion risk levels, of which 138 are in lower level of risk, 96 in middle level, 24 in higher level and 13 in very high level. A thematic map was produced using ArcGis 9.2, which shows that the townships of high risk are mainly in coastal areas where economy is relatively developed and population is bigger and more mobile.