Research On The Development Process Of The Zhibian Peatland In Changbai Mountains Since The Middle Holocene

Peatland is an important carbon pool in continental ecosystem and has a significant impact on global climate change.It is of great significance to study the development process of peatland and its relationship with regional climate and geomorphic conditions for revealing the law of carbon sequestration in peatland.Many researches have been carried out on the development process of peatland in Changbai Mountain area.At present,the development process and influencing mechanism of crater-lake peatland and weir lake peatland in this area have been revealed initially,but there are few reports on the development process of lava platform peatland.Therefore,this paper selected the branch peatland in Changbai Mountain as the research object,obtained multiple peat profiles,systematically analyzed the basement age,carbon/nitrogen/phosphorus parameters and the change characteristics of plant macrofossils of the peatland,and comprehensively reconstructed the lateral expansion and vertical evolution process of the branch peatland since 5100 cal.yr BP.The response of the peatland to local geomorphology and regional climate change is analyzed systematically,so as to reveal the development law and driving mechanism of lava platform peatland.This paper mainly draws the following conclusions:(1)The lateral expansion of the branch peatland took about 1300 years:before 4330cal.yr BP,the area was a waterlogged depression;During 4330-4030 cal.yr BP,the water body in Zhibian depression evaporated rapidly,the surface water level decreased significantly,and the peat vegetation began to colonize in the lowest terrain area.During 4030-3730 cal.yr BP,the peatland experienced the fastest lateral expansion,with the northern,eastern and southern areas covered by peat vegetation,and the expansion area reached 25.90 hm~2 during this period.During the period of 3730-3430 cal.yr BP,the peat vegetation expanded to the western region,but the expansion rate slowed down significantly,and the expansion area was 3.2 hm~2 during this period.After 3430 cal.yr BP,peatland continued to expand slowly to the northwest;At3030 cal.yr BP,the lateral expansion of the lateral peatland was basically completed,and the total area of the peatland is about 40 hm~2.(2)The vertical evolution of the lateral peatland can be divided into six stages:Before4814 cal.yr BP,the study area was a hydrostatic depression,during which the carbon accumulation rate(CAR,g/m~2/yr)was low(mean 6.79 g/m~2/yr).During 4814-4315 cal.yr BP,with the beginning of peat vegetation colonization,CAR values showed a gradually increasing trend(mean value was 25.19 g/m~2/yr).During 4315-2863 cal.yr BP,Carex gradually decreased,Betula fluctuated,CAR value increased first and then decreased(mean31.74 g/m~2/yr).During the period of 2863-1620 cal.yr BP,the number of Carex gradually increased,and the CAR value increased(mean value was 36.8 g/m~2/yr).During 1620-402cal.yr BP,Betula gradually decreased,and Carex mainly decreased,and CAR value decreased gradually(mean value was 28.07 g/m~2/yr).402 cal.yr BP-To date,CAR values reached the highest stage in 4100 years(mean 49.42 g/m~2/yr)due to the short decomposition time.(3)The sensitive component analysis of the peat ash particle size in ZB-7 profile shows that the sensitive component 2(33.36-695.43μm)can be used as a substitute index of regional precipitation.Comprehensive analysis shows that the percentage of sensitive component 2 in the period of 5109-4315 cal.yr BP is higher,indicating that there is relatively more regional precipitation.During 4315-2863 cal.yr BP,the percentage of grain-sensitive component 2 was at a low value,reflecting relatively little precipitation in the region.During 2863-402 cal.yr BP,the percentage of grain-sensitive component 2 increased again,indicating that the regional precipitation in this area increased briefly.However,due to the gradual intensification of regional dust storms since 402 cal.yr BP,the grain-sensitive component 2 cannot effectively reflect regional precipitation changes.In addition,the chroma Ca*b*value of ZB-7 profile is similar to the evolution trend of grain-sensitive component 2 of peat ash,which can be used to reflect regional precipitation changes.It is worth noting that since 402 cal.yr BP,chroma Ca*b*values have shown a slow decreasing trend,indicating that regional precipitation during this period has gradually decreased,which is consistent with other existing climate records.(4)By comparing the lateral expansion process of the branch peatland with the potential influencing factors,it is found that the lateral expansion process of the branch peatland is mainly controlled by the flat topography of the volcanic lava platform,but is less affected by the climate.The results of spectral analysis and wavelet analysis show that the carbon accumulation rate of the marginal peatland has a significant variation period of 1022 yr,709yr,200 yr and 109 yr,which is similar to the periodicality of solar radiation and El Nino activity.Due to the influence of strong solar radiation and El Nino activity,the regional temperature was higher and precipitation was higher.The vegetation community in this peatland belonged to betula--Scirpus--type community,and the CAR value increased significantly due to higher vegetation productivity.However,when the influence of solar radiation and El Nino was weak,the climate was relatively cold and dry,and the vegetation in the peatland was mainly composed of carex,while the content of Betula decreased,and the CAR value decreased due to the decreased productivity caused by the decreased content of Betula.