Impact of global warming on lake productivity in different lakes on the Qinghai-Xizang Plateau
Understanding the relationship between climate change and the lake ecosystem variations is crucial for studying the impact of global warming on the lake carbon cycling process.However,less is known of how lake eco-system variations responding to the global warming in different lakes on the Qinghai-Xizang Plateau(TP)where thou-sands of lakes distributed.Here we present comparison researches from Aweng Co(81°37'48"E～81°48'00"E,32°42'00"N～32°48'36"N,4430 m a.s.l.)and Toson Lake(96°50'00"E～97°03'00"E,37°04'00"N～37°13'00"N,2808 m),they are closed lakes with different hydrological process.Aweng Co(pH is 9.2,salinity is 29.5 g/L)is mainly supplied by glacier melt water via groundwater and precipitation.And Toson Lake(pH is 8.4,salinity is 35.7 g/L)is at the end of Bayin River drainage basin,and it is fed by precipitation and the flowing from Herleg Lake.There are villages and farmland in the upstream of the Toson Lake.Two sediment cores were drilled from the lake center in Aweng Co and Toson Lake,they were AWC2015(445 cm)and TSL17G(55 cm),re-spectively.The top sediment of AWC2015 and TSL17G were measured by 210Pb and 137Cs.We focused on the lake carbon cycling process in the two lakes in recent 100 years.Multi-proxy including organic carbon isotope,total organic carbon content and organic carbon accumulation rate were measured to reconstruct the lake pro-ductivities and carbon burial rates in two lakes.Results showed that global warming had different impacts on the photosynthetic process in different lakes depending on the lake level,actual temperature and sunlight at the lake bottom.In Aweng Co,when the values of δ18Ocarb tended to be negative,and TOC content increased,indic-ating that more glacier melt water supplied the lake,resulting in expanding of the lake area,more nutrient sup-plying the lake,and improving of the lake productivity consequently.However,when plenty of glacier melt water flowed into the lake in short time and the water temperature decreased rapidly,slowing down the photo-synthetic process and resulting in decreased carbon burial rate consequently.In the human-disturbed lake,the variations of δ18Ocarb and TOC content indicated that human activity played more important roles in driving aquatic biomass by influencing sunlight at the lake bottom via lake level change.With the increasing of water consumption for agriculture,the water that finally supplied the lake would decrease,and resulted in lower lake level and more light reaching the lake bottom,favoring the growth of the benthic algae,and the organic carbon burial rate increased finally,and vice versa.Therefore,global warming had different impacts on the carbon cycling process in lakes with different hydrological process.
the Qinghai-Xizang Plateaulakesclimate changelake productivityorganic carbon burial rate
NETL
NSTL
万方数据
