Study On Remote Sensing Identification And Early Warning Of Aquatic Invasive Plants

The invasion of aquatic exotic plants harms the ecological environment,reduces biodiversity,causes huge economic losses,and affects social and economic development.As one of the most harmful invasive aquatic plants,Eichhornia crassipes is difficult to be treated thoroughly because of its biological characteristics.Early warning is an effective means to reduce the outbreak of Eichhornia crassipes.In this study,taking Eichhornia crassipes as an example,based on news reports,meteorological data and remote sensing image data,the occurrence regularity of exotic aquatic invasive plants was analyzed,and the occurrence risk map was drawn and verified with the results of remote sensing monitoring.The work and main conclusions of this study are as follows:(1)Based on the analysis of the occurrence regularity of Eichhornia crassipes from 2011 to 2019,a total of 635 news reports were analyzed,showing a trend of rising at first and then falling,with an outbreak of Eichhornia crassipes in 19 provinces.It is mainly distributed in the Yangtze River Delta(most),the middle reaches of the Yangtze River,the Pearl River Basin,the southeast coastal area and the upper reaches of the Yangtze River in the southwest.According to the analysis,there were 124 news reports on the outbreak date,112 occurrence points,and the concentrated time period of the outbreak of hyacinth was from April to October.(2)Analysis of critical meteorological conditions of Eichhornia crassipes outbreak: the meteorological data of 30 days before the outbreak date were used to explore the meteorological law of Eichhornia crassipes outbreak.It is concluded that the critical temperature for the outbreak of Eichhornia crassipes is when the average temperature reaches 16.27 ? in the first 30 days,and the high risk temperature is when the average temperature reaches 24.05? in the first 30 days.Based on the temperature law,the risk grade of Eichhornia crassipes is divided into risk-free area(monthly average temperature <16.27?),low-risk area(16.27?? monthly average temperature ?24.05 ?),high-risk area(monthly average temperature >24.05?).(3)In order to test the early warning function of the occurrence risk map of Eichhornia crassipes,the correlation analysis between the risk map and remote sensing monitoring results in 2019 was carried out.The monthly monitoring results of Eichhornia crassipes at five monitoring points are consistent with the analysis results of monthly risk early warning of Eichhornia crassipes occurrence,so the occurrence risk early warning map of Eichhornia crassipes based on the law of air temperature is feasible.Dianchi Lake and Dianchi Lake in Shanghai entered the growth peak value of Eichhornia crassipes in December and August respectively,indicating that the biomass has accumulated continuously,but it has not yet caused the outbreak,and temperature is only a necessary and not sufficient condition for the outbreak of Eichhornia crassipes.