Study On The Relationship Between Landscape Pattern And Water Quality Threshold In Dianchi Lake Basin Considering Spatial Scale Effect

Landscape pattern is the carrier of ecological process,which determines the exchange and flow of material and energy in the landscape to a large extent.The influence of landscape pattern on the occurrence and migration of pollutants is mainly manifested as the change of surface landscape composition and spatial distribution of the basin will cause the change of material and energy flow process of the ecosystem,which changes the type and quantity of pollutants entering the river and has an important impact on the water quality of the basin.Therefore,it is of great significance to analyze the threshold relationship between landscape pattern and water quality for watershed water environment management.However,previous studies did not consider the impact of spatial scale on the threshold.Therefore,this study proposed the idea of the relationship between landscape pattern and water quality threshold considering the spatial scale effect to solve the above problems.Firstly,the percentage of landscape composition area under 9 spatial scales(riparian buffer zone and sub-basin)of 20 inflow rivers in Dianchi basin was extracted,and the optimal spatial scale of landscape pattern and water quality was identified by redundancy analysis(RDA).Then,based on this scale,Spearman correlation analysis was used to obtain the landscape pattern index related to water quality indicators.Finally,a variety of nonlinear regression models such as power regression,exponential regression,quadratic regression and piecewise regression are used to quantitatively identify the thresholds of landscape pattern and water quality.The results show that:(1)The spatial scale has a significant influence on the threshold relationship between landscape pattern and water quality,and the total interpretation rate of landscape pattern on water quality is the largest at the buffer scale of 1100m riparian zone,which is an effective buffer for river governance.(2)The influence of different spatial scales on the relationship between landscape pattern and water quality threshold is different.The number,visibility and R~2 of nonlinear regression models of landscape pattern and water quality in different periods in the buffer zone of 1100m riparian zone are better than those of sub-basins.(3)From the nonlinear relationship between landscape pattern and water quality,it is found that when the water quality changes suddenly or reaches the I–V water quality standard,the landscape threshold can be quantitatively identified.Among them,the first type of landscape threshold at the water quality mutation point can be used as the long-term goal of water quality protection in Dianchi Lake Basin,and the second type of landscape threshold can be used as the short-term goal of water quality adjustment.The research results can provide a scientific basis for the governance of water environment and the rational planning of landscape pattern in Dianchi Lake Basin,and have practical significance for guiding the sustainable development of cities.