Temporal And Spatial Patterns Of Vegetation And Lakes And Their Response To Climate Change In The Qaidam Basin

The Qaidam Basin is located in the northern of Qinghai-Tibet Plateau of China,Which belongs to the continental monsoon climate.The vegetation type is mainly desert vegetation.There are several inland lakes which are distributed in the basin.The basin is less affected by human activities and it is an important place to study the relationship between vegetation,lakes and climate change.Therefore,this paper mainly studied the dynamic change rules of basin vegetation and typical lakes and their response to climate change based on a systematic analysis of the climate changes from 1961 to 2016;At the same time,the coupling relationships and their driving forces between vegetation and lakes were analyzed in Qaidam Basin.The main results are as follows:1)From 1961 to 2016,the annual mean temperature in the Qaidam Basin has a significant upward trend,with a climatic tendency of 0.55°C/10a,which was significantly higher than the national and global mean levels in the past 50 years.The seasonal heating rates were in the order of winter>autumn>summer>spring.the climate tendency rates were 0.71°C/10a,0.55°C/10a,0.43°C/10a,and 0.41°C/10a,respectively;in the past 56 years,the annual precipitation in the basin showed a significant increase,with an increase rate of 10.95 mm/10a.Winter had the lowest growth rate,and summer was the largest.Precipitation increased rapidly in spring and autumn.Annual sunshine hours decreased at a rate of 38.4 h/10a.Spring and winter sunshine hours did not decrease significantly,but summer and autumn decreased significantly;The rate of decrease of annual mean wind speed was 0.59 m/s/10a,and the two mutations occurred in 1964 and 1988,respectively.The order of the mean wind speed in the four seasons was:spring>summer>autumn>winter,and the seasonal mean wind speed decreased obviously.2)From 2002 to 2015,the vegetation area in the Qaidam Basin increased,the vegetation coverage showed a good trend,the above ground biomass showed a significant increase,and the total carbon sink of the vegetation increased,indicating that the ecological environment of the study area tended to be better.The growth rate of vegetation area in the basin was 644.11 km~2/a;the increase rate of low coverage,medium coverage and high coverage vegetation area in the basin was300.2km~2,242.8km~2/a and 101.2km~2/a respectively;the above ground biomass of the basin was less than 1500.The low-yield vegetation of kg/hm~2 was dominant,whose area accounts for more than 90%of the total vegetation area.The rest of the vegetation was only scattered.Artificial vegetation-wolfberry mainly was distributed in Delingha,Germu,Dulan,Wulan and so on.It was estimated that the total output of the basin's main producing area would reach 1.8*10~8kg in 2017 by using high-resolution satellite.Affected by economic benefits and climate warming and humidification,the area of artificial vegetation in the basin will expand significantly after 2008.under two different warming modes in the next 50 years,it is estimated that the carbon sink potential of grassland will increase by 25.55%and 20.82%respectively.The trend of climate warming and humidification is conducive to the increase of total carbon sink of vegetation in the basin.3)Using multi-source satellite data,a lake water body area extraction model was constructed based on the lake area and the different types of remote sensing data.The analysis of the typical lake area and lake shoreline variation from east to west of the basin showed that the area of Lake Hala in the east was higher than the past.compared with the past 52 years 27.66 km2,lake shoreline change was relatively small;The area of Xiaochaidan lake in central China expanded by63.54km2 in the past 42 years.The area of Gasikale lake in the western of the basin was fluctuated irregularly from 1976 to 2017.The main reason for the extrapolation of the lake shoreline was the climate warming and humidification.Another important reason was that the basin lakes were generally shallow.The bottom of the lake is flat;In addition,the comprehensive management of the ecological environment and the construction of ecological civilization implemented by local government departments in recent years have contributed positively to the expansion of lakes and the rise of water levels.4)There is a certain coupling relationship among climate,vegetation and lake changes in Qaidam Basin:which is reflected in that the total vegetation area increases with the increase of lake area.During the 2002~2015,vegetation area of Qaidam basin and annual precipitation,the precipitation from May to September and summer precipitation are positively correlated,summer precipitation>May-September>annual precipitation,and it is negatively correlated with precipitation in autumn and winter;From 1955 to 2017,the runoff of Bayin river into the lake in the eastern part of the basin generally showed an upward trend,leading to a significant increase of area of its downstream lakes.Glacial meltwater has little effect on most lakes.After 2000,climate warming and wetting became more and more significant.Through active ecological management measures,both grassland coverage and biomass increased.Human activities have great influence on salt lake in core area of basin.