| Peatland is an important carbon pool of terrestrial ecosystems.They accumulate large amounts of organic carbon in the form of peat and are also a huge potential source of greenhouse gas emissions.In this study,we select Chi Lake(CL),Yuan Lake(YL),Dongtuling(DT)and Touxi(TX)peatlands in Changbai Mountain area for field investigation.Through high resolution in situ sampling,combined with geochemical analysis,stable isotope technique and plant macrofossil analysis,the geochemistry characteristics of corresponding peat sediments,history of vegetation evolution,greenhouse gas emissions are investigated.We explore the organic carbon accumulation and the interaction relationship between climate change and peat formation during the initial formation stage of peatlands,and the factors affecting the organic carbon accumulation and greenhouse gas emissions under natural conditions are further discussed.The main conclusions are as follows:Firstly,the results of modern peat bogs for field investigation show that the peat accumulation thickness is relatively thin in Chi Lake and Yuan Lake peatlands,and the peat at the bottom layer which was formed much earlier has higher decomposition degree.In particular,the fire events happened at the bottom of the Yuan Lake seem to cause the rapid decomposition of peat.Chi Lake is characterized with the alternating growth of Cyperaceae and Sphagnum as the dominant plants,while there was shrubs growing in Yuan Lake in the early form of peat,later with the transition to Cyperaceae and Sphagnum.According to the environmental indicator plants,Yuan Lake behaves a wetting trend towards now.Combined with the analysis from peat decomposition indices and plant macrofossil results,we find that the increase of wetness in peatlands slows down the decomposition rate of peat,revealing that the peat decomposition degree is affected and controlled by hydrological conditions,and the wetness trend of climatic and hydrological conditions is conducive to the rapid accumulation of organic carbon.Secondly,the results of field investigation in Dongtuling and Touxi peatlands show the deep peat sediments and high organic carbon content.The peat decomposition degree in two peatlands generally decreased at first and then increased.The main reason could be that the decomposition rate of peat in the surface exposed to air is faster due to the fluctuation of the groundwater level,while the decomposition degree in the bottom was related to historical temperature,changes of dry and wet environment as well as longer deposition time.The observation results of greenhouse gas in the underground of peat show that the concentration of CO2 and CH4 in the deeper peat is much higher than that in the surface,and there are higher peak concentrations of CO2 and CH4 in the shallow layer of peat.The main reason for the peak concentration of greenhouse gases in the shallow layer is that the shallow layer of peat is an active area for the decomposition of organic carbon,and the shallow layer is easily affected by the hydrothermal conditions.Therefore,it can be inferred that climate change can have a great impact on the decomposition process of peat in the shallow layer of peatlands,and thus affect its greenhouse gas emission process.In conclusion,the investigation of four peatlands in the Changbai Mountain region shows that the Chi Lake and Yuan Lake peatlands with a relatively short development time have lower organic carbon in the bottom,but with the continuous accumulation of peat and the increase of environmental wetness,the preservation and accumulation of peat are promoted.The results of greenhouse gas emission in Dongtuling and Touxi peatlands indicate that the shallow layer of peat is an important area for active peat decomposition process and could be vulnerable to change of hydrothermal conditions.These peatlands have very high organic carbon content,and the future climate change will play a key role in peat decomposition and greenhouse gas emissions. |
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