| Global warming has become one of the major environmental problems in the world.Climate warming causes changes in the combination of temperature and humidity at various latitudes,resulting in changes in surface vegetation composition.As a sensitive indicator of environmental response,peatland contains extremely rich information on environmental changes,and is regarded as a good geological archive in paleoenvironment research.As a kind of micro-paleontology with strong corrosion resistance and long-term preservation in sediments,testate amoebae can sensitively react to changes in water table and pH of peatlands.Changbai Mountain is located in the temperate monsoon climate zone in northeastern China.It is a concentrated distribution area of peat swamps in China,as a sensitive area for environmental changes.In this study,a 100 cm peat core was sampled from the Laolike peatland(42°28?32? N-42°28?46? N,128°39?34? E-128°40?9? E;1470 m a.s.l)in the Changbai Mountains.The chronological model was established using radioactive nuclides dating methods,namely 210Pb/137 Cs and AMS14 C dating.Based on testate amoebae data,the peatland water-table and pH variations were quantitatively reconstructed using a transfer function during the last 2000 years.It invert the past environmental evolution process of peatland,and comparatively analyzes the relationship between the past water-table and pH of peatland.Trying to explore the driving factors affecting the past water-table and pH of peatland.The main conclusions are as follows:1.A total of 100 samples were identified in this paper.A total of 50 species of testate amoebae were identified,and the number of shells was 16,880.The main species are:Hyalosphenia sp.,Centropyxis aculeata type,Heleopera petricola/sphagni,Assulina muscorum,Phryganella acropodia,Arcella hemisphaerica,Difflugia lucida,Arcella discoides type,Centropyxis aerophlia type,Trigopyxis arcula,Cyclopyxis arcelloides,Trinema complanatum,Difflugia oblonga type,et al.2.Based on the established testate amoeba-environmental factor transfer function model in the Changbai Mountain area,combined with the characteristics of the species combination of testate amoebae species in the Laolike peat profile,the depth to water table and pH of the peatland since 2000 are reconstructed.The results of the reconstruction show that the Laolike peatland has been generally wet during the past 2000 years,it has experienced a relatively wet-very moist-more humid change process.The pH of the peatland has been generally weakly acidic,and has undergone an acidic-weakly acidic-strong acidic change.3.According to the characteristics of the testate amoebae species on the peat profile and the results of constrained clustering,the environmental change process of the peatland was divided into the following three stages:(1)7-107 AD(100 cm-93 cm)peatland was relatively humid.In acidic environments,testate amoeba are mainly wet-loving and indicating weakly acidic environment species,and dry-drying/ indicating strong acidic environment species are few.The water table fluctuates more frequently.The fluctuation of 4.4 cm from the surface water drops to 8.9 cm below the surface.The pH value drops from 6.29 to 5.73.(2)107-1776 AD(93 cm-28 cm)peatlands are very moist and the acidity is weakened.The ground surface retains standing water for a long period of time,and the depth to water table is basically lower than 0 cm,but the depth of standing water is continuously shallow.The pH value is high,staying between 6.30-6.10.Wetness/indications dominate weakly acidic species.(3)1776-2017 AD(28 cm-0 cm)Although the peatland has been significantly dried from the previous stage,it is still moist and has increased acidity.The water table continued to drop from 0.2 cm to 5.2 cm,and the fluctuation of pH 5.78 decreased to 5.39.Species suitable for moderate humid conditions and moderate acidity predominate,and species that are wet and indicate a weakly acidic environment have decreased significantly.4.The comparison found that the past water table and pH of the Laolike peatland showed a significant negative correlation(r=-0.918,p<0.001).The changes in the past water level and pH of the peatland are affected by the common factors of endogenous process and climate change.The fluctuation of its water level causes the species composition of peatlands to change,and the acidity of the peatlands. |
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