Through the data comparative analysis of three large scale surveys in Lechang city, the exotic plants species had increased by almost 40% during recent 25 years, and the growth showed an accelerating tendency. The populations of exotic plants also presented a rapid growth, espedcilly increased rapidly, the harmful invasive plants had also increased rapidly. especially the harmfulness exotic plants, such as Alternanthera philoxeroides, Ambrosia artemisiifolia and Lolium temulentum, etc.The analysis showed that the reasons of those changes included improvement of local transportation condition, increasing of trade and economic, tourism and introduction activities, and the impact of climate change. There were following strategies should be adopted to reduce the harmfulness of exotic plants on local plants. The invasive plants defense system should be established as soon as possible. Meanwhile, the surveys should be conducted and the range of propaganda work should be expanded. Finally, invasive species risk assessment system and rapid response system should also be established.
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