Effects Of Permafrost Degradation On Moisture And Nutrients Of Typical Vegetation And Soil In The Da Xing'an Mountains And Xiao Xing'an Mountains

In recent years,due to climate warming,permafrost degrades,the Da Xing 'an Mountains and Xiao Xing 'an Mountains are very sensitive to climate change,hydrology,topography and geomorphology will change correspondingly,affecting vegetation community diversity and leading to changes in vegetation productivity.Therefore,this paper intends to study the effects of permafrost degradation on vegetation-soil moisture and nutrients in Da Xing 'an Mountains and Xiao Xing 'an Mountains,and then reveal the response mechanism of permafrost degradation to vegetation-soil ecological processes.Based on the construction and simulation of the SFI freezing index model,permafrost degradation is represented and analyzed in the form of calculating the area of different types of permafrost.Using the method of replacing time series with space series,according to the three types of permafrost regions simulated by the 2020 model,Samples were collected and analyzed from three kinds of marsh wetlands in the permafrost region(Mohe),the large discontinuous island permafrost region(Heihe),and the forest swamp,scrub swamp and meadow swamp in the discontinuous island permafrost region(Wuyiling).Based on ANOVA,RDA,Pearson correlation analysis and Kriging spatial interpolation,the influence factors of vegetation-soil moisture and nutrients and the relationship between permafrost degradation and vegetation-soil moisture and nutrients were studied.The main conclusions are as follows:(1)Using MODIS images in 2000,2010 and 2020 to build and simulate the SFI freezing index model,analyze the permafrost degradation in the Xing 'an Mountains.Permafrost in the Da Xing 'an Mountains and Xiao Xing 'an Mountains has a trend of moving from south to north.The discontinuous island frozen soil is gradually increasing.The variation of large discontinuous island frozen soil area fluctuated most obviously,showing a trend of first increasing and then decreasing.For many years,the fluctuation of frozen soil area is large,showing a gradually decreasing trend.(2)The vegetation-soil moisture and nutrient contents showed different trends from the early stage to the middle stage to the late stage of wetland succession.Vegetation organic carbon and total nitrogen showed a trend of gradual increase,total phosphorus showed a peak trend,and water decreased as a whole.Soil organic carbon,total nitrogen,total phosphorus and moisture showed different trends,in which soil organic carbon and moisture showed a trend of gradual increase,total phosphorus showed a peak trend,and total nitrogen showed a trend of overall decrease.(3)The kriging interpolation model combined with auxiliary information was used to interpolate soil C,N,P and water content.It was found that with permafrost degradation,soil C,N,P and water content in the study area increased to varying degrees,gradually increasing from the north to the south.(4)With permafrost degradation,vegetation moisture and nutrients generally increased,and the effects of soil carbon and phosphorus on vegetation nutrients gradually weakened,while the effects of available nitrogen,phosphorus and potassium,soil moisture,temperature and elevation on vegetation nutrients gradually increased.The effects of temperature,soil C,N,P and elevation on vegetation water content gradually increased,while the effects of available potassium and PH on vegetation water content gradually weakened.