Study On Ecosystem Stability Of Peatland In Jilin Longwan National Nature Reserve

Although peatlands cover only about 3%of the global land area,their carbon stocks are one-third of the global terrestrial carbon stocks.Therefore,peatlands play an important buffering role in addressing global climate change.In recent years,China is facing the problem of significant reduction in the area of peatlands,more serious loss of wetland degradation and a serious weakening of wetland service functions.For China,maintaining the stability of wetland ecosystems and ecosystem service functions has become a major issue that needs to be urgently addressed in the process of wetland management.As the largest distribution area of peatlands in China,the important role of the Northeast region is self-evident.In terms of water containment and soil conservation,the peatland in the source areas of the Changbai Mountains,which are located in the valley depressions,play an important functional value,and the stability of their ecosystems also determines the ecological security and food security of the downstream of the watershed.This paper focuses on the stability of the typical peatlands,Jinchuan Peatland ecosystem,in Jilin Longwan National Nature Reserve,by using the frequency analysis method,expert consultation method and the"Peatland ecosystem stability evaluation index system"constructed with reference to local standards.This study systematically analyzed the changes of Jinchuan peatland in terms of structure,function and external environment during the decade by means of field sampling survey,remote sensing data interpretation and combined with years of hydrological monitoring data.In addition,the Analytic Hierarchy Process(AHP)and coefficient of variation(CV)were used to assess the ecosystem stability status of Jinchuan peatland and to judge the possible future change trends of the peatland based on the results of indicators at all levels.After the evaluation and comparative study,the following conclusions were drawn.(1)From the perspective of the structure of Jinchuan peatland,there were significant differences in the structural characteristics of Peatland plant community,water level and soil physical and chemical properties during the decade.The Detrended Correspondence Analysis(DCA)and TWINSPAN community classification showed that there was a change in the dominant species in the Jinchuan peatland,which was dominated by wet plant communities,but gradually began to coexist with grasses and shrubs.This is consistent with the increase of woody plant cover.In contrast,the shrubs gradually spread from the periphery to the center.In Jinchuan peatland,the species composition of the two periods differed by 39.44%of the total number of species and were mostly mesophyte.The main factors affecting species diversity changes in the wetland were soil p H and water level.During the decade,there were significant differences between interannual and monthly mean water levels in the peatland.In particular,water levels in the peatland were significantly higher in 2020 than in 2011(p<0.05).Although water levels were higher in 2020,water levels fluctuated dramatically during the year.Compared to 2011,there was high spatial heterogeneity in water level variability among regions within the wetlands.Soil organic carbon(SOC),C/N ratio and N/P ratio increased with increasing soil depth.There were no significant differences in total soil nitrogen(TN)and total phosphorus(TP)under different soil profiles.The nutrient levels in Jinchuan peatland showed a gradual decreasing trend during the decade.The SOC and C/N ratios also showed a decreasing trend during the decade,which indicated that the surface peat of the peatland was gradually decomposing.(2)From the perspective of Peatland function of Jinchuan peatland,the carbon sequestration function decreased the most significantly,by 25.81%.The trend of change between the two indicators of material production function was different.Among them,the mean peatland NDVI values showed an increasing trend.The peak NDVI distribution indicated that woody plants contributed more to the NDVI values,while the dry biomass of herbaceous plants showed a decrease.Dry biomass variation showed a non-significant negative correlation with the water level.During the decade,the wetland storage capacity of Jinchuan peatland has been decreasing,which is mainly due to the decrease of peak water level and saturation water holding capacity of wetlands and the change of soil physicochemical properties.The carbon stock of the Jinchuan peatland was reduced by 0.32×10~8t,which was directly influenced by the change of soil SOC content,capacitance and above-ground biomass.(3)The external environment in which the study area is located has changed significantly during the decade.From the change of land use type,the land use type of the Hou River Basin,to which the study area belongs,has changed.Among them,the area of dry fields has increased significantly.Around the Jinchuan peatland are filled with a large number of dry and paddy fields,and the artificial river channels and drainage canals at the wetland boundaries block the hydraulic connection between the wetlands and the river,thus destroying the ecological integrity of the peatland.In this case,the water recharge of Jinchuan peatland has to be replenished mainly by atmospheric precipitation.The results of the linear regression analysis between water level and precipitation in the previous month also proved a positive correlation between the two.The decreasing trend of the standardized precipitation evapotranspiration index(SPEI)over the 30-year period indicates a decreasing trend of moisture variability in the study area.The moisture status of the peatland varied between"moderately wet-normally wet-lightly wet-lightly wet"during the decade,which is consistent with the semi-humid and semi-arid climatic characteristics of the region.In the seasonal variation of moisture,there is a decreasing trend in summer,which is the period with the highest precipitation during the year.In the long term,the water recharge of Jinchuan peatland is not optimistic.(4)During the decade,the Jinchuan peatland ecosystem was relatively stable,and the greater variability in the criterion layer was external environment(CV:0.15-0.22).In the case of climate change and land-use type change,the structure and function of peatland remain relatively stable.The stability coefficient of each indicator is basically between 0.85 and 1.00,with the greater variability being the annual water level change indicator(CV=0.32).According to the positive correlation between precipitation and water level,it is known that in the context of future global climate change,the external environment can influence the change of peatland water level through the change of precipitation.Altering the physical and chemical properties of peatland soils may become an important factor threatening the hydrological storage function,the carbon sequestration function of peatland,and even the overall stability of peatland.