Study On The Influence Of Plant Community Structure Change On The Stability Of Soil Carbon Pool In Permafrost Region

Under the background of global warming,The permafrost wetland in the Great Hing'an Mountains is facing the trend of degradation,which leads to great changes in the wetland ecological environment.Climate warming will significantly change the community structure and biodiversity of wetland plants in permafrost area,which will have a certain impact on the carbon input,accumulation and output process of ecosystem.In this study,shrub-sedge wetland in different permafrost zones of the Great Hing'an Mountains was taken as the research object.The changes of plant community structure and the stability of soil carbon pool in different permafrost zones were studied,and the effects of plant community structure changes on the stability of soil carbon pool were revealed,and provides a scientific basis for further understanding the process and mechanism of wetland carbon cycle in permafrost region under the background of climate change.The main results are as follows:(1)There were differences in plant community structure in different types of permafrost zones.From large continuous permafrost wetland to sporadic island permafrost wetland,the species richness of plant community first decreased while the diversity and evenness increased,then the plant richness increased,and the diversity and evenness tended to be stable;According to the calculation results of ? diversity of plant communities,it was shown that the similarity of plant communities between large continuous permafrost wetland and discontinuous island permafrost wetland was larger,while the similarity between the two zones and sporadic island permafrost zones was smaller,which indicated that the spatial heterogeneity of sporadic island permafrost wetland environment was relatively larger.The biomass in sporadic island permafrost wetland was largest,indicating that temperature is still an important factor affecting the growth of wetland plants,and climate warming will increase the aboveground biomass of wetland in permafrost zones.(2)The total carbon(TC)content of soil from large continuous permafrost wetland to sporadic island permafrost wetland decreased gradually;he chemical composition and structural features of soil organic carbon in different permafrost wetlands were similar,mainly including four obvious resonance regions: alkyl carbon,alkoxycarbon,aromatic carbon and carboxyl carbon,but the proportion of each functional group was different,on the whole,the proportion of alkyl carbon and alkoxycarbon were significantly higher than that of aromatic carbon and carboxylcarbon,and the proportion of alkoxycarbon,alkylcarbon/alkane and aromatic-carbon/alkoxycarbon of wetland soil in sporadic island permafrost zones were significantly higher than that in large continuous permafrost zones and discontinuous island permafrost zones,indicating that the stability of soil organic carbon structure in sporadic island permafrost wetland was relatively lower.The change of mineralization rate of soil organic carbon with temperature accorded with exponential function at different soil depths,the temperature sensitive coefficient Q10 of surface soil organic carbon mineralization was as follows: large continuous permafrost wetland > discontinuous island permafrost wetland > sporadic island permafrost wetland,which indicated that the response of surface soil to global warming tended to be more sensitive from sporadic island permafrost wetland to large continuous permafrost wetland.(3)There was a positive correlation between the total carbon(TC)content and the important value of evergreen shrub,a negative correlation between TC content and Margalef index,community biomass and the important value of deciduous shrub,and a negative correlation between DOC content and Margalef index.The stable component of soil organic carbon chemical composition,alkyl carbon,was negatively correlated with Margalef index and plant community biomass,while the unstable alkoxycarbon was positively correlated with Margalef index,community biomass and important value of deciduous shrub,but negatively correlated with important value of evergreen shrub;Compared with the large continuous permafrost wetland,the wetland in sporadic island permafrost zones had larger plant biomass,higher richness,larger proportion of deciduous shrubs,lower total carbon content of soil and higher rate of carbon mineralization,which showed that under the background of global warming,the stability of soil carbon pool in permafrost wetland has a decreasing trend.