Study On Wetland Landscape Pattern Evolution And Landscape Ecological Risk In Water Network Region

The existence of ecological risk restricts the upper limit of urban sustainable development,and landscape ecological risk assessment has increasingly become an important basis for regional development and construction.However,the special wetland landscape pattern in water network area puts forward new requirements for traditional landscape ecological risk assessment methods.With the regional integration of the Yangtze River Delta becoming a national strategy and the water network region as its core development region,it is urgent to use targeted landscape ecological risk assessment as a reference for landscape ecological planning in this region.The purpose of this study is to optimize the landscape ecological risk assessment method in water network area based on the evolution characteristics of special wetland landscape pattern in water network area.Wujiang District of Suzhou City,a typical water network area,is selected as the research object,and three time sections are taken in 2008,2012 and 2016.From the landscape dynamic model,the spatial pattern of landscape pattern index,morphology analysis of water network region three angles of typical wetland landscape pattern evolution law,based on the analysis results to optimize ecological scale of regional landscape ecological risk assessment methods,finally,the ecological dimension,administrative measure,quadrat scale evaluation results are compared,Verify the scientific nature and applicability of the optimized evaluation method,and then put forward the corresponding landscape ecological risk control strategy.The main research contents and results are as follows:(1)Build a landscape dynamic model from four aspects to explore the stability of wetland landscape dynamic change.From 2008 to 2016,the wetland landscape area in Wujiang District decreased significantly,and the decreasing trend slowed down gradually.In Wujiang District,the characteristics of landscape type transfer changed from "block" to "fragmentation" after the removal of counties and the establishment of districts.Landscape dynamic model indexes of lake wetland and river wetland were the most stable in the whole stage.(2)To explore the correlation of wetland landscape change trend by analyzing the change of wetland landscape pattern index.From 2008 to 2016,the wetland patches in Wujiang District tended to be fragmented as a whole.At the same time,the small patches were getting smaller and the large patches were getting larger.Within the scope of the study,lake-river-tidal wetland,ditch wetland-field and ridge landscape,paddy wetland-dry land landscape,pit and pond wetland-woodland landscape,and construction land-road landscape had a strong correlation in the change trend of type level index,and the landscape in the same group had similar ability to resist external risk disturbance.(3)Based on the stability and correlation of wetland landscape dynamic change,the water network texture in Wujiang District was identified,and the spatial distribution pattern and law of water network texture were explored by morphological spatial pattern analysis.It was found that the river and lake wetland were the main components of water network texture,while the other landscape types were the secondary components.The power-law distribution characteristics of the two types of ecological core areas are significant,which verifies the rationality of the extraction method,and also indicates that the core area represents the coupling range of landscape pattern and ecological process.Thus,three major water network morphological regions can be divided:In addition,we analyzed the significant difference of the "rank-size" distribution law of the ecological core area in the disc-shaped depression area,the lakeside network area and the inland branch area.(4)Optimize the vulnerability index of the landscape ecological risk assessment model through the correlation of landscape change trends,divide the key ecological core area of water network texture as the ecological scale evaluation unit according to the landscape ecological risk assessment method of optimized water network area,and find:According to the results of landscape ecological risk assessment in Wujiang from the ecological scale,the landscape ecological risk index in Wujiang from 2008 to 2016 showed a slight decrease and then a significant increase trend,with low risk areas and high risk areas as the main areas,and the distribution of risk levels showed a strong spatial agglomeration.The risk value ranking of the three water network morphological zones is as follows: lakeside network area >dish-shaped depression area > inland branch area;From the perspective of administrative scale,the risk level of towns and municipalities is relatively low,and the risk level of villages along Taihu Lake is relatively high,while the risk level of inland villages is relatively low.From the quadrat scale,the area of the middle risk region was the most sensitive to the quadrat size,while the area of the low risk region and the very low risk region did not change significantly with the quadrat size.The comprehensive comparison of the evaluation results of multiple scales verifies the scientific nature of the optimization method and its applicability in water network area.(5)Based on the analysis of wetland landscape pattern evolution and landscape ecological risk assessment results in Wujiang District,the landscape ecological risk control strategy of Wujiang District is proposed from the ways of combining local and temporal measures,top-down and bottom-up measures,and internal optimization and regional coordination.