The Exotic Plants Of Urumqi City

Five hundred and twelve species of exotic palnts belonging to 102 families and 332 genera are identified and recorded on Urumqi city through investigation. Among them, fern plants has 7 species belong to 4 families and 4 genera, gymnosperms has 13 species belong to 6 families and 11 genera, angiosperms has 492 species belong to 92 families and 317 genera. Most exotic plants belong to a relatively few families, such as composite (Compositae), liliaceous(Liliaceae),rosaceous(Rosaceae),leguminous(Leguminosae)etc, which has close relationship with the main purpose of the exotic plant introduce into Urumqi city for urban greening and family viewing. There are 512 species exotic plants in Urumqi, including 34 species vicious exotic plants, which were recorded in the list of China's Main Foreign Weed Species announced by State Environmental Protection Administration of China(SEPA) in 2002 and other regional literature in China, such as (Solidago Canadensis L. )and (Eichhornia crassipes (Mart.) Solms. )And so on.Intentional introduced by human being is the main pathway for exotic palnt imported to Urumqi, this kind of exotic plant mainly be used for urban greening , family viewing and agricultural production, there totaled have 481 species, are 94 percent in total exotic plants in Urumqi. Only 31 species are unintentional introduced through human activities and proportion to 6% of all exotic plants. Investigations revealed, they were mainly had no intention of introducing into Urumqi with the plants migration, particularly with the introduction of cultivation of garden plants. The analysis of introduction time indicated that the exotic plants have been introduced since ancient times, and exotic plants augmented as the international and interprovincial exchanges grow.Investigations revealed, the exotic plants mainly distribution and occurred in the urban areas in the semi-protection or the protection of cultural habitats in Urumqi City. From the urban to the suburbs and then to the outskirts, both the number and variety of exotic plants are rapid reduction, and there are almost no exotic plants distribution under the wild conditions. The occurrence and distribution of the exotic plants in Urumqi City were mainly influenced by three factors: water situation and anthropogenic interference and the capacity of spread of self-propagation. Among them, water is the most important limiting factor on impact the occurrence of exotic plants. Therefore, the Urumqi City, even Xinjiang region as a whole, the regions with good moisture conditions or those mountainous areas are most likely subject to exotic plants invasive.Synthetize the results of field investigation and comprehensive literature search, there are 6 species exotic plants have a higher invasive risk, these exotic plants has been established self-sustaining population in Urumqi, such as (Conyza Canadensis (Linn.) Cronq.), (Galinsoga parviflora Cav.), (Hibiscus trionum L.), (Euphorbia maculata L.), (Amaranthus retroflexus L.), (Cynanchum chinense R. Br.). There are 2 species (Oenothera biennis L.) and (Oenothera glazioviana Mich.) Has invasive risk on Urumqi. Although there are 5 species exotic plants do not establish self-sustaining populations in Urumqi, but there have potential invasive risk, such as (Amaranthus viridis L.), (Phytolacca americana L.), (Erigeron annuus (L.) Pers.), (Xanthium spinosum L.), (Avena fatua L.). In addition, 2 species with low invasive risk in the XinJiang region, but they still needed further study and observe to confirm they risks of invasion.