Modelling Holocene Carbon Accumulation Dynamics In Peatands,Changbai Mountain

As an important part of the carbon cycle of terrestrial ecosystem,peatland has the ability to sequester carbon for a long time and is a very important carbon reservoir,plays an important role in the global carbon cycle.China's Changbai mountain region is located in a typical east Asian monsoon climate zone,and its unique temporal and spatial distribution and peatland ecosystem have also recorded high-resolution information of paleoenvironmental changes,making this region an ideal place to study peatland's response to global climate change.However,the relationship between carbon accumulation patterns in peatlands and climate change remains unclear.Therefore,exploring the response of peatland carbon accumulation to climate change will provide an important basis for future research on peatland.In this paper,Laolike and Hengshan peatlands in Changbai mountain area were selected as the research object,and the dynamic changes of carbon accumulation in peatlands were discussed by measuring the physical and chemical indexes of peat and combining AMS14 C and 210 Pb / 137 Cs dating techniques.Three decomposition models were used to fit peat profile data,the short scale and long scale carbon accumulation patterns were described,and the response of peat carbon accumulation patterns to climate change was further analyzed.The main conclusions are as follows:?1?the variation range of the recent carbon accumulation rate?RECAR?in the Laolike peat profile is 36.8-235.1g m^-2yr^-1,with an average of 88.7g m^-2yr^-1.The RECAR variation range of Hengshan peat profile is 13.5-254.8g m^-2yr^-1,with an average of 98.7g m^-2yr^-1.The carbon accumulation rate of the two peat profiles increased with time,which was consistent with the organic carbon content.The carbon accumulation rate of these two peat profiles has increased more significantly in the last 20 years than in the early peat formation.The Long term carbon accumulation rate?LOCAR?of the Laolike peat profile since the holocene ranged from 9.5-82.7g m^-2yr^-1,with an average of 35.2 g m^-2yr^-1.The LOCAR variation range of Hengshan peat profile is 3.1-62.3g m^-2yr^-1,with an average value of 28.5g m^-2yr^-1.The high carbon accumulation rates(71.9g m^-2yr^-1and 59.1g m^-2yr^-1,respectively)in the old rick and hengshan peat profiles in the early holocene may be due to high solar radiation and intense summer monsoon activity.After 2.5 cal.ka BP,the carbon accumulation rate increased significantly and reached its maximum in the last few hundred years.This may be because in the lateholocene,the combination of cold and wet climate is not conducive to the decomposition of peat,and the peat formed in recent centuries has not undergone good carbonization and post-decomposition.?2?The decomposition model was used to fit the two profiles measured by 210 Pb,both of which presented concave peat mass-age curves.This may be because in the late holocene,the climate showed the characteristics of cold and wet,the decomposition rate was low,and the input rate was constant,so that the peat profile presented a concave accumulation pattern.The two peat profiles determined by14 C presented an s-shaped wave curve.The decomposition model was used to fit the two sections in sections,and the results showed that the Laolike peat profile was divided into 5 sections:?1?24-94cm?concave??2?94-137cm?concave??3?137-220cm?convex??4?220-327cm?con vex??5?327-491cm?concave?.The Hengshan peat profile is divided into 5 sections:?1?37-132cm?concave??2?132-223cm?convex??3?223-299cm?concave??4?299-338cm?c onvex??5?338-370cm?concave?.Reasons for formation: continuous reduction of input rate or continuous increase of decomposition rate leads to a convex carbon accumulation pattern;The concave accumulation pattern of peat profile is due to the constant input rate of peat.?3?A single exponential decomposition model(p=118g m^-2yr^-1,k=0.01yr^-1)was used to test the sensitivity of peat input rate?p?and decomposition rate?k?for peat profile data of acrotelm layer.The results show that under the condition of constant input rate,increasing decomposition rate will cause the curve to move upward?the peat accumulation decreases?.At a constant decomposition rate,a reduction in the input rate would cause the curve to move upwards?a reduction in peat accumulation?.Compared with the decomposition rate,the input rate has more influence on the accumulation of peat.Taking the peat profile of the catotelm layer of Hengshan peat as an example,the sensitivity analysis shows that the change of the input rate of peat will significantly affect the "young" peat and "older" peat,and reduce the input rate of peat and make the curve move upward?reduce the accumulation of peat?.The rate of decomposition has a much greater effect on "older" peat than on "younger" peat.