A Multi-scale Study On The Relationship Between Land Use Landscape Pattern And Water Environment Quality

Wetlands are an important part of ecological sustainable development.The quality of water environment not only determines the ecological efficiency of wetlands,but also reflects the effectiveness of regional ecological protection.Land use landscape pattern is not only a comprehensive reflection of human activities,but also an important factor affecting water pollution.Therefore,the study on the response relationship between wetland water environment quality and land use landscape pattern characteristics can not only provide support for the construction and management of wetlands,but also provide important theoretical and practical significance for regional water environment protection and improvement and landscape planning.Based on the remote sensing images and digital elevation(DEM)data of Yangcheng Lake wetland,this study analyzed the water environment quality characteristics and multiscale land use landscape pattern of Yangcheng Lake wetland by using the spatial analysis,sub-watershed division and Fragstats software of Arcgis software and the results of water quality monitoring.Spearman correlation analysis,redundancy analysis(RDA)and partial least square(PLS)were used to construct the statistical relationship model of land use type,landscape pattern index and water quality index,to quantitatively explore the influence of landscape composition type and landscape spatial structure on wetland water environment quality,and to reveal the scale effect of land use landscape pattern on Yangcheng Lake wetland water quality.Interactions mainly draw the following conclusions:(1)From the characteristics of land use types,on the spatial scale,the proportion of lake area decreased with the increase of buffer radius;the proportion of urban residential land and aquaculture pond area increased gradually with the increase of buffer radius;the proportion of Arbor woodland area showed the opposite trend of gradual decrease.In the sub-watershed scale,the area of Arbor woodland and paddy field is relatively large,while that of lakes,aquaculture ponds and urban residential land is relatively small.(2)According to the characteristics of landscape pattern,the combination degree of landscape patches is higher in 100 m buffer zone.The fragmentation degree of patch type increased in 200 m buffer zone.In the 500 m buffer zone,the patch density((PD))and the maximum patch index((LPI))decreased.In the 800 m buffer zone,the maximum plaque index(LPI)and sprawl index(CONTAG)decreased slightly,while the number of patches(NP)and maximum shape index(LSI)increased.In the 1000 m buffer,the number of patches(NP)increased.In the sub-watershed scale,the number of patches in the middle of the basin as a whole(NP)is relatively low,and the difference of patch density(PD)is large,indicating that the degree of landscape fragmentation is low.In the southwest of the basin,the maximum patch index((LPI))is lower and the landscape shape index((LSI))is higher.(3)According to the spatial distribution characteristics of water quality,there are great differences among different water quality sampling points in Yangcheng Lake wetlands.The low concentration values of most water quality indexes are mainly distributed at D4 in the northern part of the West Lake and D9 in the middle part of Lianhua Island in Yangcheng Lake.The distribution of urban residential land,paddy fields and aquaculture ponds near these points is less than that of other sites.The most polluted areas are D2 in the middle of West Lake,D10 in the south of Lianhua Island in Yangcheng Lake,D11 in the middle of East Lake and D12 in the north of East Lake.The proportion of Arbor woodland in the buffer zone where these points are located is relatively low,while the area of paddy fields and lakes is relatively high.(4)From the influence of different scale land use types on wetland water environment quality,in the small buffer zone of 100-500 m,urban residential land has a greater impact on wetland water environment quality.In the 800-1000 m buffer zone,the Arbor woodland has a great influence on the water environment quality of the wetland.The order of scale dependence of land use types on water quality is as follows: sub-watershed > 100 m buffer zone > 1000 m buffer zone > 800 m buffer zone > 500 m buffer zone > 200 m buffer zone.The influence of land use types on water environment quality in Yangcheng Lake Wetland Subbasin is in the following order: Lake > urban residential land > Arbor woodland >aquaculture pond > paddy field.(5)From the influence of different scale landscape pattern index on wetland water environment quality,only patch number(NP),patch density(PD)and landscape shape index(LSI)have significant correlation with individual water quality indexes in 100 m buffer zone.In the 200m-1000 m buffer zone,patch density(PD),patch combination degree(COHESION),landscape patch index(LPI),sprawl index(CONTAG)and Shannon diversity index(SHDI)have certain effects on water environment quality.In the sub-basin scale,LSI,SHDI and SHEI have a strong negative impact on most water quality indicators,while LPI and CONTAG have a greater positive impact on most water quality indicators.The order of scale dependence of landscape pattern characteristics on water quality is as follows: sub-basin > 500 m buffer zone > 200 m buffer zone > 100 m buffer zone >800m buffer zone > 1000 m buffer zone.The influence of landscape pattern index on the water quality of Yangcheng Lake is in the following order: SHDI > LPI > LSI > SHEI >COHESION > CONTAG > PD > NP.(6)Based on the research results,the optimization and promotion strategy of Yangcheng Lake wetland is put forward.At the landscape level,the land use and landscape spatial layout within the wetland buffer scale and sub-basin scale should be allocated reasonably;at the ecological level,the management of urbanization should be strengthened,urban ecological construction should be promoted,agricultural pollution control should be strengthened,agricultural industrial structure should be adjusted,purse seine aquaculture management should be improved,and sustainable recycling should be realized.On the social level,improve the water quality of wetlands,implement the legal system of wetland protection,adhere to the harmonious symbiosis of human and wetlands,and promote the sustainable development of wetlands.