| With the development of economy, the progress of science and technology, thecommunication between countries in the world becomes more frequent and the contactbecomes more closely. With the globalization of the culture, information and economic, theinvasion success rate of the alien species has greatly increased. It is difficult to control that thepopulation of some exotic species has been increased greatly, after their invading successfully.Not only they destroy the local ecological system, causing local species diversity, geneticdiversity and ecosystem diversity decreasing, while they cause the Agriculture ForestryAnimal Husbandry and fishery huge economic loss and have a threat to human health.Biological invasion has been the second major reasons which lead to global biodiversity loss,and is also one of the three biggest and the most difficult environmental problems.Alternanthera philoxeroides originates from South America. Since the nineteen thirties,Alternanthera philoxeroides has been introduced into Shanghai as horse feed by Japaneseinvasion. After it is promoted cultivation as pig and sheep feed in the southern provinces inthe nineteen fifties, many escaped disaster resulted in grass. Alternanthera philoxeroides is aperennial herbaceous plant. Not only its vitality is very strong, but it has a wide adaptabilityand can also propagate quickly in a short time. It can grow both in the Terrestrial environmentand the aquatic environment and grow rapidly in the latter. It often covers the waters, clogswaterways, effects of freshwater aquaculture and farmland irrigation, endangers human healthbecause of in the breeding of a large number of flies and mosquitoes in the river, and damagesto city landscape. Therefore, it becomes one of the world recognized malignant weed.In2003,it has been included in the State Environmental Protection Administration published" Chinathe first batch of alien invasive species list", and becomes a typical kind of alien invasivespecies.As a result of Alternanthera philoxeroides unique ecological stress tolerance andnutritional reproductive mode, the current various control methods are difficult to thoroughlyand effectively manage and the control cost of Alternanthera philoxeroides is very big,therefore it is more effectively and economically to prevent the invasion instead of controllingafter its outbreak. It is the original intention of this paper to predict future diffusion region ofAlternanthera philoxeroides and take its control measures in advance.At present, there are many ecological risk prediction models based on climate forpredicting potential distribution of species. In fact, this article forecasts the potentialdistribution of Alternanthera philoxeroides in China based on GARP niche model and MAXENT maximum entropy model. At first, this article divides the potential distribution intofive risk levels: serious threat zone (OV≥90%), potential threat zone (70%≤OV <90%),suitable growth zone (50%≤OV <70%), growth zone (30%≤OV <50%), not suitable growthzone (OV <30%), where OV representing the overlap value at GARP niche models, theappearance probability of species in every grid at the MAXENT maximum entropy models.And then evaluates two by using ROC curve. According to the AUC value, combine these twokinds of prediction results to a more accurate prediction result by giving GARP weight 0.8,MAXENT weight 0.2. The third, after comprehensively analyzing the potential distribution ofAlternanthera philoxeroides in our country, divide the country into 5 risk levels according tothe percentage of threatened zone occupying respective provinces: threatened zone (thepercentage≥99% ), diffusion zone (90% < the percentage < 99% ), suitable zone (50% < thepercentage≤90% ), growth zone (0 < the percentage≤50%), safety zone (the percentage =0).At the end, provinces at different level of risk propose different prevention measures. Theresults show that, Hongkong, Shanghai and Jiangsu is in the threatened zone; Guangdong,Guangxi, Jiangxi, Fujian, Anhui, Hunan and Zhejiang is in the diffusion zone; Guizhou,Henan, Hubei, Chongqing, Yunnan and Taiwan is in the suitable zone; Shandong, Hainan,Sichuan, Shaanxi, Hebei, Shanxi, Gansu and Tibet, these eight provinces is in the growth zone;the remaining 9 provinces is in the safety zone. In the threatened zone and diffusion zone, themain task of the provinces is to manage and eliminate Alternanthera philoxeroides organs.The main task of the provinces In the suitable zone and growth zone is to control the outflowof Alternanthera philoxeroides organs and prevent species from outbreak, while the main taskof the other provinces in the safety zone is mainly publicizing the damage of alien speciesinvasion, strengthen the people of ecological consciousness. |
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