Study On The Relationship Between Soil Physical And Chemical Characteristics And Vegetation Characteristics In Different Types Of Frozen Soil Regions In The Huma River Basin

Permafrost and vegetation occupy a high proportion in the cold region ecosystem.Due to the influence of environmental change,temperature rise and other factors,the permafrost region has a high frequency of freeze-thaw,and the permafrost region soil,vegetation and other indicators have significant changes because of the rapid degradation of permafrost.The permafrost region of Huma River Basin is the high latitude permafrost region of the Northern Hemisphere.The continuous permafrost region（R-CP,R-CP,Continuity 50-90%）,discontinuous island permafrost region,R-DIP,Continuity is 10-50%),sporadic island permafrost region（R-SIP,continuity<10%）.In this paper,by means of field investigation and remote sensing monitoring,permafrost areas with different fragmentation degrees in the Huma River Basin are selected as research objects to study soil physical and chemical indexes,vegetation community characteristics and vegetation coverage,and to study the relationship between permafrost degradation and soil properties and vegetation characteristics in the high-latitude permafrost areas combined with the influence of climate and topography.This paper further reveals the interaction between soil and vegetation in different types of permafrost areas,so as to further study the effect mechanism of the degradation of permafrost caused by climate change on the ecosystem of the Xingan Range-Beijiahu type,and provide scientific theoretical basis for the follow-up study of ecology in cold areas.The main conclusions of this paper include:（1）There are significant differences in soil physicochemical properties in different types of frozen soil.Soil organic carbon（SOC）and dissolved organic carbon（DOC）in continuous permafrost areas were significantly higher than those in discontinuous island permafrost areas and sporadic island permafrost areas（P<0.05）.The contents of ammonia nitrogen（NH₄⁺-N）and nitrate nitrogen（NO₃^--N）in continuous permafrost areas were significantly lower than those in discontinuous island permafrost areas and sporadic island permafrost areas（P<0.05）.The soil acidity of the three types of permafrost areas was acidic,and the acidity decreased with the decrease of permafrost continuity（P<0.05）.The overall soil water content of the study area was higher,and the water content（SWC）of sporadic island permafrost area was significantly higher than that of continuous and discontinuous island permafrost area（P<0.05）,but there was no significant difference between continuous and discontinuous island permafrost area（P>0.05）.（2）There are significant differences in vegetation characteristics in different types of permafrost areas,and permafrost degradation has a positive effect on vegetation growth.Vegetation composition changes from deciduous coniferous forest to deciduous broadleaved forest with the decrease of permafrost continuity.The average canopy density and vegetation coverage increased significantly in turn,and the average canopy density and vegetation coverage of R-SIP were 47%and 77%respectively.The mean vegetation density of R-DIP was 44%,and the mean vegetation coverage was76%.The average vegetation canopy density of R-CP was 46.2%,and the average vegetation coverage was 75%,indicating that the decrease of permafrost continuity had a positive effect on vegetation growth.（3）There are significant changes in vegetation remote sensing indexes of different types of frozen soil,and the decrease of permafrost continuity has a positive effect on vegetation coverage,which is conducive to extending the growing season.In the study area,both NDVI and EVI are at a higher level,and the sporadic island permafrost area is higher than the continuous permafrost area,indicating that the decrease of permafrost continuity is conducive to the increase of vegetation coverage.For grassland,broadleaf forest,coniferous forest and inner river valley in the northeast and southwest of the study area,the values of NDVI and EVI in the former are higher,while the values of NDVI and EVI in the latter two are lower.And within these regions,the spatial features have similar characteristics.The existing NDVI cannot completely correct the atmospheric influence,and there is a high probability of saturation and other phenomena in areas with high vegetation coverage.The spatial pattern of EVI tends to be consistent with vegetation type,so as to monitor the permafrost area of Huma River Basin more effectively.（4）The main influencing factors of vegetation characteristics in different types of frozen soil are different,which are mainly affected by soil physicochemical properties.With the degeneration of frozen soil from R-CP to R-SIP,permafrost gradually changes from a high-stress environment to a more adaptable environment.The correlation between vegetation and soil NO₃^--N and NH₄⁺-N decreases,and shows a high correlation with soil water content.The p H is consistent with the dominant vegetation characteristics of the transition from deciduous coniferous forest to deciduous broadleaved forest.And lead to soil SOC,DOC content decreased.From the perspective of zoning,SOC,p H and NH₄⁺-N are closely related to the vegetation in continuous permafrost area,while NO₃^--N and p H are strongly related to the vegetation in discontinuous island permafrost area.SWC and SOC are related to the vegetation in sporadic island permafrost area to a certain extent.