Study On Ecological Risk Assessment And Early-Warning Of Weigan-Kuche River Delta Oasis

With the rapid increase of population and ineffective allocation of resources,the self-adjustive ability of ecological system is weakened,so that human's living environment is getting worse and we have to take more risks than ever.Based on this,we chose the Weigan-Kuche River Delta Oasis,one of the typical alluvial floodplains in Northwest China,as the study area.It made a ecological risk assessment and a early warning for the Weigan-Kuche River Delta Oasis by using remote sensing method and technology,combining remote sensing image,field observation data and DEM,Land use map,socio-economic data and other datas.The land use/cover landscape of the study area was extracted by monitoring the classification of the remote sensing images of the region in the same season in 1989,2001,2007 and 2013,and the landscape pattern dynamics of the study area were analyzed and predicted.Then,the ecological risk index of the study area was evaluated by the ecological risk index constructed by the landscape pattern index.Finally,the ecological early warning index and the BP neural network algorithm was used to construct the early warning model of ecological risk in the study area.The main conclusions were as follows,1)In the past 25 years,the Land use/cover types had not changed,but the area and proportion of land use/cover types changed greatly.The whole tendency is the surely increasing of oasis,the cultivated land was 41.74 × 104hm2 in 2013.The transformation between cultivated land and grassland is more significant,reaching a maximum of 14.32 × 104hm2.The landscape fragmentation of the study area showed a decreasing tendency from 1989 to 2013.The intergranular aggregation was enhanced,the connectivity of the largest dominant landscape was also increased,and the heterogeneity of the landscape increased slightly,but the number and area ratio of each patch type were unbalanced development.2)The CA-Markov model was used to predict the landscape distribution of the oasis of the Weigan-Kuqa River Delta Oasis in 2019.The overall change trend is still the expansion of the oasis area,reaching 55.48 × 104hm2.The landscape is manifested as an increase in woodland and saline land,and reduction of grassland.Since 1989,the ecological risk degree of the study area had the trend of decrease.The lowest and lower risk areas were mainly distributed in the oasis area which mainly consisted of cultivated land in the study area,While the higher and high risk areas are mainly distributed in mountainous area,sandy area,serious salinization area where there was much unused land and could not regarded as human activities area.3)Based on the comparison with the linear regression analysis prediction model,the BP neural network method with model fitting degree of 0.9886 was used to establish the ecological risk early warning model of the Weigan-Kuqa River Delta Oasis.Through the early warning model,the ecological risk of the oasis in the Weigan-Kuqa River Delta Oasis in 2019 is consistent with the actual trend in the early stage,and the overall trend is decreasing.However,the ecological environment of the oasis,especially the saline soil and other land-use areas,is still relatively poor,with the high ecological risk.It is necessary to effectively control and improve this area in order to improve the overall ecological environment of the study area.Ecological risk research of the Weigan-Kuche River Delta oasis which is extremely unstable to the ecosystem can promote the local people's understanding of ecological risks,and help the government function part to carry on the effective management to the ecological risk.The study has a positive effect on the rational development of regional land and the sustainable use,also the protection of the ecological environment.