Reasearch On The Characteristics Of Microorganisms And Organic Carbon Mineralization And Their Influences During The Recovery Of Secondary Quercus Variabilis Forest In The Karst Region

As an important driving factor of soil carbon pool,vegetation recovery in the karst region can obviously influences the preservation and loss of soil carbon pool,while microorganism plays a key role in the mineralization decomposition of organic matters by microorganisms in soil carbon cycle.Although domestic and foreign scholars have widely discussed and explored the dynamic changes in the soil organic carbon pool during the vegetation recovery in the karst region recently,there are few researches deeply understanding the interrelation between the characteristics of soil organic carbon mineralization and microorganisms during vegetation recovery in the karst region.Therefore,deep researches on the change features and interrelation between soil organic carbon mineralization and microorganism are of great significance to promote vegetation recovery in the karst region and improve the ecological service functions of the ecosystem in the karst region.Taking the secondary quercus variabilis forest with five different recovery terms in the karst region in Zhechuan County as the research objective,applying indoor mineralized culture,high-throughput sequencing and other technology and adopting the method of replacing time with space,this research analyzes the dynamic characteristics of soil physicochemical property,soil microflorae and organic carbon mineralization,so as to explore the mutual effect between soil organic carbon mineralization and microorganism during vegetation recovery.The main results of this research are shown below:(1)The secondary quercus variabilis forest has low volume weight of soil and bad soil condition in the research area.When the recovery term is 40 years,the community structure reaches the best state,and Shannon index,Simpson index,Pielou index and various soil chemical indexes are the maximum.(2)During the recovery of quercus variabilis in the karst region,species diversity increases with the recovery term,while species uniformity experiences a process of first increase and then decrease;when the recovery term is 30 years,species diversity and uniformity are the most.When the recovery terms are 20 years,30 years,40 years,50 years and 70 years,the secondary quercus variabilis forest includes 85 fungal communities and 1826 bacterial communities respectively on genera level,which occupy the vast majority and have few unique genera.Besides,Agaricamycetes,Sordariomycetes and Eurotiomycetes are the dominant species of fungi,and Proteobacterias,Acidobacteria,Actinobacteria and Chloroflexi are the dominant species of bacteria.According to the results of one-way variance,it is indicated that there are great differences in the type of bacteria among Actinobacteria,Chloroflexi,Patescibacteria and Gemmatimonadetes in the soils with five different recovery terms on phylum level,and there is no great difference in the type of fungi in the soils with five different recovery terms on class level.(3)During the recovery of quercus variabilis in the karst region,the rate of soil organic carbon mineralization and carbon mineralization potential will be the maximum if the recovery term is 40 years,and the order of the turn-around speeds of organic carbon pool with different recovery terms is: 40 years> 70 years > 50 years > 30 years > 20 years.When the recovery term is 40 years,the carbon cycle in the soils of quercus variabilis is faster,and there are more carbon sources for microorganisms to absorb;the soil is more suitable for the existence of microorganisms.(4)According to RDA sequencing,during the vegetation recovery of quercus variabilis in the karst region,CEC and water content exert the most influence on the distribution of bacterial communities;the biggest factor influencing the distribution of fungal communities is total potassium content in the soil and soil carbon mineralization.According to the analysis of multiple linear regression,it is indicated that during the vegetation recovery of quercus variabilis in the karst region,the main factors influencing organic carbon mineralization potential are organic carbon content and effective nitrogen content,and the richness,evenness and diversity of microbe species in the soil exert no direct influence on the organic carbon mineralization,which shows that microorganism communities in the karst regulate the organic carbon mineralization process through regulating the environmental factors in the soil.On phylum level,the dependency among Glomeromycota,environmental factors and organic mineralization indexes is the strongest,which can be used to indicate the soil organic carbonmineralization condition in the karst region.