Spatial And Temporal Distribution Of Wetland Vegetation In Sugan Lake Basin And Its Genetic Analysis

Wetland is a unique ecosystem with a special eco-hydrological process and highly heterogeneous environment,the special environmental characteristics of the water-land interface are the main factors that determine the succession stage,structural stability,health status and ecological service function of wetland ecosystem.Inland salt marsh wetland has a unique eco-hydrological process,plant functional area of the composition and structure,the spatial distribution of wetland types and plaque evolution characteristics,as well as the spatial heterogeneity of vegetation coverage and stability and its environmental response mechanism,understanding under the background of global change,the terrestrial ecosystem service function and structure stability maintaining mechanism is of great significance.The Sugan lake basin is a typical and representative inland salt marsh wetland in the northern margin of the Chaidamu basin,which belongs to the inland alpine and semi-arid climate.Vegetation has formed unique regional ecological characteristics in the process of long-term adaptation to cold,drought and soil salinization.In this paper,by using remote sensing,wetland vegetation investigation and the environmental factor correlation analysis method,studies the Sugan lake basin to advantage spatial heterogeneity and the evolution pattern of wetland plants,wetland types and its main patch,the fragmentation of environmental response relationship,spatial and temporal variation characteristics of vegetation coverage,explore the inland salt marsh wetland plant functional traits and the ecological geography basis of the formation of wetland types and provide theoretical basis for wetland protection and utilization of resources.The following research results are obtained in this paper:(1)The Sugan lake area and the Dangzhong spring area are located in the lower reaches and middle reaches of the Haerteng river system respectively,and there are differences in the dominant plant composition and spatial and temporal distribution characteristics.In Sugan lake area,compared with 1987 in 2017,Leymus secalinus area in general is on the decline,the variation coefficient is 0.17,the areas of Phragmites australis and Triglochin palustre showed an overall increasing trend,and the coefficient of variation was 0.08.In Dangzhong spring area,compared with 1987 in 2017,Triglochin palustre first decreased and then stabilized,with a coefficient of variation of0.1,Leymus secalinus increased first,then decreased,then increased,and the coefficient of variation was 0.1,Carex first decreased,then increased and then decreased,with a coefficient of variation of 0.15.(2)From 1987 to 2017,the area of wetland in Sugan lake area did not increase significantly,and the area of wetland in Dangzhong spring area decreased by 29.48%due to siltation and quicksand burial.The variation of wetland type area in Sugan lake and Dangzhong spring area showed different trends.The inland salt marsh,fresh water spring,river wetland and brackish marsh in Sugan lake area generally decreased,while the grass marsh,bog meadow and lake wetland increased.Compared with 1987 in 2017,the inland salt marsh wetland,freshwater spring,river wetland and marshy meadow in Dangzhong spring area showed an overall decrease trend,while the herb marsh showed an overall increase trend.(3)In the Sugan lake area,there is a pattern of mutual transformation among wetland types,in the inland salt-marsh wetland,marshy meadow,herbaceous marsh,lake wetland and brackish marsh,the patch separation degree is on the decline,the fragmentation index is on the decline,the integrity and connectivity are increased,and the freshwater spring and river wetland show the opposite change characteristics.In Dangzhong spring area,wetland,sandy land and desert were mainly transformed,and wetland types were transformed into auxiliary ones.In the inland salt-marsh,herbaceous marsh and river wetland,the patch separation degree was decreasing,fragmentation index was decreasing,and the integrity and connectivity were increasing.(4)Influenced by the spatiotemporal evolution of dominant plants and wetland types,the FVC in the Sugan lake area increased from 23.57% to 32.37% from 1987 to2017,with an increase rate of 38.90%.The change with low and lower FVC were generally decreasing,while the change with medium,higher and high FVC were generally increasing.The FVC in area Dangzhong spring increased from 18.82% in1987 to 24.01% in 2017,with growth rate of 27.58%.The change of low FVC area generally shows a decreasing trend,while the change of lower FVC,medium FVC,higher FVC and high FVC area generally shows an increasing trend.(5)There is a difference in FVC change trend between the Sugan lake area and the Dangzhong spring area.FVC in the Sugan lake area decreased from 1987 to 2002 and increased from 2002 to 2017,while FVC in the Dangzhong spring area decreased from1987 to 2007 and increased from 2007 to 2017.The stability order of FVC of different grades is as follows: in Sugan lake area,the high FVC< medium FVC<low FVC< lower FVC< higher FVC,in Dangzhong spring area,the lower FVC<high FVC< medium FVC<low FVC< higher FVC.(6)From 1987 to 2017,the temperature and precipitation in the sugan lake basin showed an upward trend,and the annual rate of change was 0.2 ? · 5a-1 and 0.85 mm · 5a-1 respectively,the groundwater depth in the Sugan lake area and the water system density in the Dangzhong spring area both showed a downward trend.The correlation between precipitation and the distribution area of dominant plants was greater than that between temperature and the distribution area of dominant plants.There was a significant correlation between groundwater and the distribution area of three plants in the Sugan lake area.The water system density in the Dangzhong spring area was only significantly correlated with Carex.The influence of groundwater depth on wetland type area in Sugan lake area is greater than that of precipitation and temperature,and the influence of precipitation on wetland type area in Dangzhong spring area is greater than that of temperature and water system density.The study area is an alpine and cold area,and the increase of temperature is conducive to the increase of vegetation coverage.The increase of precipitation,groundwater depth and water system density will reduce the vegetation growth area and have a negative impact on the vegetation coverage.