Study On The Stability Of Soil Organic Carbon Pool And Its Relation With Plant And Microbial Diversity In Bayinbulak Alpine Wetland

Alpine wetlands in arid regions plays an important role on maintaining ecological stability and system function.In recent years,due to the impact of climate change and human activities,alpine wetlands in arid regions have experienced degradation succession in varying degrees,which leads to the "unlocking" of organic carbon,the core of soil quality.Based on the typical succession sequence of alpine wetlands(swamp-swamp meadow-meadow)in Bayinbrook arid area,this study used spatial distribution instead of time series to study the effects of succession of alpine wetlands on vegetation diversity,soil physical and chemical properties,aggregate stability,carbon pool composition,microbial diversity and function from the perspective of ecosystem ecology.Revealing the relationship between plant diversity,soil aggregates,microbial biological activity and soil organic carbon pool stability.The results are as follows:(1)Plant biomass(118 g·m-2),coverage(67%),species number(9 species)and species diversity(Shannon-Weiner index 2.99)were the highest in all succession areas in the seasonal water-logged swampy meadow area(SM area).The biomass(85 g·m-2)and coverage(38%)of the perennial flooded swamp(SP area)were the second,but the species number(2 species)and species diversity(Shannon-Weiner index 0.97)were the lowest.The biomass(40 g m-2)and coverage(30%)of temporary flooded meadow were the lowest,followed by species number(6 species)and species diversity(Shannon-Weiner index 2.56).The individual proportion and coverage ratio of Cyperaceae in the community were the highest in SM area,followed by SP area,and the lowest in M area,namely SM area>SP area>M area.The proportion of Gramineae was M>SM>SP.(2)The variation trend of TOC(93-128-53 g·kg-1)was the same as that of TN(7.5-10-5 g·kg-1),C/N(12.2-12.7-10),and AN(96-119-45 mg·kg-1)in the succession sequence(SP-SMM),namely SM>SP>M.Redundancy analysis of vegetation characteristics and soil physical and chemical properties(RDA analysis)showed that environmental variables such as TOC,TN and AN were positively correlated with biomass,coverage and the proportion of Cyperaceae in community.Soil pH,conductivity and redox potential were positively correlated with plant species diversity,Gramineae and weeds.(3)The results of high-throughput sequencing showed that the bacterial diversity of SM region(OUT,1249;Shannon-Weiner index,5.82)was the highest,followed by SP region(OUT,1107;Shannon-Weiner index.5.80),and M region was the lowest(OUT,950;Shannon-Weiner index,5.35).The diversity of fungi showed a decreasing trend along the succession sequence(SP-SM-M:OUT,502-473-336;Shannon-Weiner index,4.07-4.02-3.10).RDA analysis showed that acidobacterium,nitrifying spirulina,sclerenchyma,ascomycetes and basidiomycetes of eutrophic bacteria were positively correlated with soil total organic carbon TC,active carbon pool(LFOC),total nitrogen TN and aggregate stability,while phytoplasma,bacillus and actinomycetes of poor trophic bacteria were more resistant to stress,and sacculomycetes of fungi were positively correlated with soil total organic carbon TC,active carbon pool(LFOC),total nitrogen TN and aggregate stability.Soil pH,bulk density and inert carbon pools(mSOM,fPOM)were positively correlated.Bacterial functional gene abundance analysis showed that bacterial functional gene abundance in SP and SM regions tended to divide and increase cell value,while bacteria in M region tended to survive on their own,that is,uptake and metabolism of nutrients.(4)Soil enzyme activity increased gradually with the succession sequence(SP-SM-M)(Gmea,10-25-40).Soil basic respiration and enzyme activity also increased gradually(SR,80155-160 g·m-2·d-1).Microbial carbon content increased first and then decreased(MBC,160550-245 mg·kg-1),while metabolic entropy decreased first and then increased(Mq,0.33-0.200.28).The diversity of carbon source utilization was SM>SP>M(Shannon-Weiner index:4.85-4.50-4.46).Redundancy analysis showed that soil enzyme activity was positively correlated with soil basic respiration,coarse-grained carbon components were positively correlated with microbial metabolic entropy,microbial biomass carbon and carbon source utilization diversity were positively correlated with soil total organic carbon,light organic carbon and aggregate stability,and microbial biomass nitrogen was positively correlated with soil fine-grained carbon components and mineral-bound carbon components.(5)The stability of soil aggregates in SM area is the highest,with the average weight diameter of MWD 4.35 mm,followed by SP area,MWD 4.18 mm,and the stability of M area is the lowest,MWD 3.48 mm,that is,SM area>SP area>M area.The bound carbon content of aggregates with different particle sizes increased first and then decreased with succession(SP-SM-M),namely SM>SP>M.In SM region,more active light organic carbon(LFOC)and granular organic carbon(iPOM-C)are retained,which are 18%and 40%respectively,while the inert carbon component-mineral bound carbon(mSOM-C)in M region is higher,which is 60%.Carbon content of fine iPOM in SM region and M region with non-anaerobic succession is higher than that of coarse iPOM,while that of SP region without succession is in anaerobic state of accumulated water.Carbon content of coarse iPOM is higher than fine iPOM.(6)Redundancy analysis showed that the higher the biomass,coverage and the proportion of Cyperaceae,the stronger the stability of carbon pool.The relationship between plant diversity and carbon pool stability is not significant;acidobacterium,nitrifying spirochete and sclerenchyma of eutrophic bacteria,ascomycetes and basidiomycetes of fungi contribute greatly to the stability of soil carbon pool;the higher the genetic diversity of bacteria,the stronger the stability of soil carbon pool;the higher the soil microbial biomass carbon,the higher the diversity of carbon utilization,the more stable the soil carbon pool.In conclusion,the swampy meadow in arid alpine wetland has high biomass,plant diversity,microbial diversity and aggregate-bound carbon and activated carbon pools,while the above indicators are significantly reduced from degraded succession to meadow stage.Therefore,the protection and long-term dynamic monitoring of Alpine humidity in Bayinbrook arid area should be further strengthened.