| Wetlands is the important part of terrestrial ecosystem,which has a lasting ability of carbon storage and carbon fixation.Despite covering only 6-8% of the world's land surface,the amount of carbon(C)stored in wetland has been estimated to be one-third of the global organic soil C pool,which plays a significant role in global C cycles.Northeast China is the largest freshwater wetlands area in China,with extensive peatlands in mountain regions and across the plains,and mainly affected by the East Asian summer monsoon,the widely distributed peatlands have formed a large C pool.How did they accumulate such a huge amount and highly climate sensitive carbon during the past thousands of years? How did they participate in the global carbon cycles in different historical stages,and what factors affect the carbon accumulation process? These problems have been a hot research field.Northeastern China is located in one of the sensitizing ranges on the earth,and its unique geographical location and wetland ecosystems sensitivity responds to climate change,which make it as an ideal testing ground for the study of C accumulation response to global climate change.However,the relationship between wetland initiation,C accumulation and climate controls is still poorly documented and understood.Understanding the responses of these C-rich ecosystems to past climate change will provide useful insights into projecting the fate of wetland C in the future.Based on the important role of wetlands in the global C cycle process,the study of wetland C accumulation is becoming an urgent task in the current.In this study,we make the northeast China wetlands as the research project and provide a synthesis of C accumulation records in northeast China.Through the AMS14 C,210Pb and 137 Cs dating methods to established the wetland profile chronology framework,we demonstrate the temporal and spatial patterns of wetland initiation and development histories across this region and elucidate the influence of regional climate history on peatland initiation and C dynamics.The purpose of this study is to reconstruction the wetlands C accumulation rate in northeast China and discusses the wetlands C accumulation rate response to the regional climate,and fully assessment of wetland ecological system in the influence and function of the balance of regional carbon.The main conclusions are as the follows:(1)In this study,we present a detailed historical reconstruction of wetlands development in northeast China based on 312 basal peat dates,and examine the relationship between Holocene wetlands dynamics and climate sensitivity.Our results indicate that wetlands initiation started in the early Holocene and that the majority of peatlands were initiated by and developed during the late Holocene,which is very different from the timings for other major northern peatland regions.During the early Holocene,due to the high insolation and stronger monsoon intensity,the climate is warm and humid in northeast China,which led to the wetland formation and development,while in the late Holocene,the widespread peatland initiation in the late Holocene might have been caused by the cool and moist climate patterns,which was concomitant with decreasing insolation and monsoon intensity,which also supports the hypothesis of accelerating initiation and growth of the northern peatlands in the late Holocene.In addition,the optimum timing of the peatland development was not uniform across northeast China,and these spatial-temporal differences indicate the influences of regional climate and terrain on peatland initiation.Both temperature and humidity are important factors influencing the wetland initiation in this region.(2)In this study,we calculate the wetland C accumulation in northeast China based on 107 basal peat dates.The results show that the Holocene long-term apparent rate of C accumulation(LORCA)ranged from 5.74 to 129.31 g C m-2 yr-1,of which the range change relatively larger,with an average rate of 37.2 g C m-2 yr-1.The peak LORCA occurred during the early Holocene,probably in response to higher temperatures and stronger East Asia summer monsoon intensities,after that the LORCA gradually decreased.The increasing LORCA over the last 2.0 ka,especially the higher rates in the last few centuries,may be explained partly by low rates of decomposition of the newly formed peats.Moreover,this change trends also showed a similar patterns of that in northern China peatlands and other northern peatlands in the world.In addition,we find the values of LORCA since 2.0 ka range from 8.78 to 94.55 g C m-2 yr-1 in northeast China.The C accumulation rate since 2.0 ka in northeast China is highly variable from site to site,but displays a significant North-South trend of decreasing accumulation at higher latitudes.Furthmore,we also find that total C accumulated over the last 2.0 ka is linearly related to photosynthetically active radiation over the growing season(PAR0),supporting the hypothesis that rates of net primary productivity(NPP)are more important than decomposition rates in determining long-term C accumulation.(3)In this study,we used core data from 134 peatland sites and the Second National Wetland Resources Survey data to estimate C storage and calculate the wetland area across northeast China.The results show that the total wetland area and C storage within this region is 82,870 km2 and 4.34 Gt C,and about 80% of the C is contained in Mountain wetlands,such as Changbai Mountains,Great Khingan Mountains and Lesser Khingan Mountains,while the Plain wetlands just store 20% of the C.Based on the core data and the Second National Wetland Resources Survey data,we estimated that the total peatland covered an area of about 10,520 km2 on the Sanjiang Plain(SJP)and currently stores ~0.73 Gt C,which is an important C pool.However,due to the human activities,together with the widespread warming on the SJP over the past 60 years,which caused extensive wetland loss and degradation and results in the loss of soil organic carbon,and the entire SJP region has switched from a carbon sink to a significant carbon source. |
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