Landscape Pattern Evoluting And Driving Forces Of Alpine Wetland In Swan Lake, Bayanbulak

The changes in landscape pattern of alpine wetland ecosystem,one of the special ecosystem in arid areas and attracted global attentions.In the context of global warming,the ecological hydrological process is bound to change,so what is the trend of the alpine wetland landscape pattern in the arid area?What factors have caused the landscape pattern to change?Taking Swan Lake alpine wetland in Bayanbulak as the research area.Thus,the goal of this study is to investigate the evolution characteristics of landscape pattern between years and within years,and reveal the changing trend of wetland landscape pattern,then,identify the relationship between climate factors and wetland landscape pattern was preliminarily revealed.We uses maximum likelihood method to extract wetland information from five remote sensing images in 1996-2015 and six remote sensing images in May-October 2015.At the same time,combining with Bayanbulak meteorological data and topographic factor data,and transfer area and landscape pattern index and mathematical statistics to analyses Swan Lake alpine wetland in Bayanbulak.The conclusions could provide theoretical reference for the protection of the ecological environment of alpine wetland in arid region and the selection of image data for the analysis of landscape pattern evolution.The main results are as follows:(1)The landscape shows a pattern of "summer stability-Autumn sharp decline" in the alpine wetland of Bayanbulak Swan Lake.During the growing season,the areas of wetland varied from 74.23%to 81.15%of total area before August.However,the wetland area decreased by 38.97%after August.At the landscape level,the landscape fragmentation and the spatial heterogeneity increased during 5-8 months.At the same time,the shape of patches tended to be complex.However,the landscape fragmentation and the spatial heterogeneity decreased during 9-10 months.Simultaneously,the shape of patches tended to be simple.At the class level,the fragmentation of wetland patches increased and the shape of patches tended to be complex.(2)These results indicated that the wetland in Bayanbulak Swan Lake degraded and the environment of the wetland became worse during 1996-2015.In the past 20 years,the area of the wetland decreased by 5.62%during 1996-2015 with the rate is 1.91 km2·a-1.The changes of the wetland area can be divided into two periods over 2010.Before 2010,the percentage of wetland area in Bayanbulak Swan Lake ranged from 77.24%to 78.26%.After 2010,the wetland area continued decreasing at a low speed and the area decreased by 5.28%.At the landscape level,the landscape fragmentation and the spatial heterogeneity increased during 1996-2015.Furthermore,the shape of patches tended to be complex.At the class level,the fragmentation of wetland patches increased and the shape of patches tended to be complex.(3)Monthly mean temperature was a major factor in the stability of the alpine wetland landscape patterns in the Bayanbulak Swan Lake.During the growing season,with the increase of precipitation,temperature increases,wetland area increases and fragmentation decreases;with the decrease of precipitation,temperature decreases,wetland area decreases and fragmentation increases.daily maximum temperature have a greater impact on the landscape pattern evolution of Swan Lake Alpine Wetland in Bayanbulak than other factors.In the past 20 years,the area of the wetland tended to be stable with the increase of the daily maximum temperature and the changes of fragmentation degree were not obvious when the daily maximum temperature was below 18.7℃.In contrast,the area of wetland decreased and the fragmentation increased with the increase of the daily maximum temperature when the daily maximum temperature was over 18.7℃.(4)During the growing season,the center of gravity of Swan Lake Alpine Wetland in Bayanbulak tends to migrate alternately from northwest to southeast,and the track of center of gravity forms was a "Z"shape.Wetland patches are randomly distributed in space.In the past 20 years,the center of gravity of Swan Lake Alpine Wetland in Bayanbulak shifted alternately from northwest to southeast,and the track of center of gravity formed a was "Z" shape.Wetland patches are randomly distributed in space.