Effects Of AMF On The Characteristics Of Soil Organic Carbon Components Under Different Land Use Types In Meadow Grassland

Soil organic carbon pools are an important part of the global carbon cycle,and changes in their accumulation and decomposition directly affect the global carbon balance.The changes in land use not only affect the capacity and level of carbon fixation in the terrestrial ecosystem,but also indirectly affect the content and distribution of soil organic carbon through factors that affect the formation and conversion of soil organic carbon.AMF community structure and colonization characteristics are closely related to soil organic carbon.However,the AMF diversity,growth and development status,colonization characteristics,and the composition and distribution of soil organic carbon under different land use and different soil depths are still lacking in understanding.An in-depth study of the effects of AMF on the composition and distribution of soil organic carbon pools will help people understand the dynamic biological processes of soil carbon pools.This study was conducted in Changling County,Jilin Province,south-central Songnen Grassland,characteristics and spatial distribution of organic carbon components in soil?forest soil,grassland soil?high and low diversity?,farmland soil?corn and bean??under different land use patterns?0-100 cm soil layer?as the research object.Through field experiments,we compared the horizontal and vertical distribution of soil total organic carbon?TOC?,microbial biomass organic carbon?MBC?,easily oxidized organic carbon?EOC?,water-soluble organic carbon?WSOC?,particulate organic carbon?POC?,light fraction organic carbon?LFOC?,and heavy fraction organic carbon?HFOC?under different land use methods,and analyzed the effects of land use on soil organic carbon composition and spatial distribution characteristics;we further compared the content and distribution of AMF community composition,growth and development status,colonization characteristics,and glomalin?GRSP?under different land use types to clarify the impact of land use types on AMF growth and development.Then we analyzed the correlation between AMF related factors and soil organic carbon composition and distribution characteristics,and initially revealed the impact of AMF on soil organic carbon composition and distribution under different land use,and finally discussed the effects and possible mechanisms of AMF on soil organic carbon composition and distribution characteristics under different land use types.1.In the 0-100 cm soil layer,the TOC content in each soil layer was represented as forest> moderately degraded grassland>healthy grassland>corn farmland>bean farmland.The soil HFOC,LFOC and POC of five land-use types had a greater influence on the TOC content,and the content of the these three soil organic carbon components in each soil layer is forest>two grasslands>two farmland,especially for soil HFOC,it's distribution pattern in each soil layer under five land use types was the same as the TOC distribution pattern.The soil HFOC,LFOC,and POC of the five land use types had the highest soil content in the surface layer?0-10 cm?,and showed a downward trend with the increase of soil layer depth.Especially in the 0-30 cm soil layer,its content decreased significantly.The proportion of soil MBC,EOC and WSOC to TOC content was relatively small,and the content in two farmland soils was the lowest in each soil layer;and the overall change trend of its content in the 0-100 cm soil layer decreased with the increase of the soil depth,but the content of each soil layer fluctuated.2.Under different land use methods,the aggregates of soil particle sizes of 0.053-0.25 mm,0.25-0.5 mm and 0.5-2 mm account for a relatively large proportion in each soil layer.In the 0-60 cm soil layer,the mass percentage of aggregates with a soil particle size of 0.053-0.25 mm from large to small: forest>corn farmland>bean farmland>healthy grassland>moderately degraded grassland;In the 60-80 cm soil layer,the mass percentage of aggregates with a soil particle size of 0.053-0.25 mm from large to small: forest>bean farmland>corn farmland>healthy grassland>moderately degraded grassland.In the 0-20 cm soil layer,the mass percentage of aggregates with a particle size of 0.25-0.5 mm in bean farmland is significantly higher than other land use types?P<0.05?;in the 20-80 cm soil layer,moderately degraded grassland and healthy grassland soil particle size mass fraction is significantly higher than other land use types?P<0.05?.The mass percentage of aggregates with a particle size of 0.5-2 mm in each soil layer from large to small: moderately degraded grassland>bean farmland>corn farmland>healthy grassland>forest.Among all soil layers,the mass percentage of 0-0.053 mm aggregates in bean farmland soil was the highest.However,the percentage of soil particle size>2 mm was not different in each soil layer.In the 0-100 cm soil layer,the MWD values of the moderately degraded grasslands in each soil layer were significantly higher than other land use types?P<0.05?,and there was no significant difference in the GMD values of each land use type?P>0.05?.Except for forests,the MWD values of other land use types are negatively correlated with soil POC and HFOC content.3.In the 0-90 cm soil layer,spore?density?SPD?appeared as forest>healthy grassland>moderately degraded grassland>bean farmland>corn farmland;hyphal?length?density?HLD?showed the highest in forest,no significant difference between healthy grassland,moderately degraded grassland and bean farmland,but significantly higher than corn farmland.In the 90-100 cm soil layer,SPD and HLD showed no significant difference between forest,healthy grassland and moderately degraded grassland,and were significantly higher than that of corn farmland and bean farmland.In the 0-10 cm soil layer,mycorrhizal colonization?MC?appeared as forest>bean>healthy grassland>moderately degraded grassland>corn farmland;in the 10-20 cm soil,there are no significant differences in the five land use types.Under different land use types,SPD,HLD,and MC decreased with increasing soil depth.Under the five types of land use,SPD,HLD and MC all had extremely significant positive effects on TOC,POC and HFOC.HLD and MC in bean farmland,and SPD,HLD and MC in moderately degraded grassland and corn farmland all had a positive effect on soil MBC content.Forest soil SPD,HLD and MC all had a significant negative effect on soil MBC content.The SPD,HLD and MC of healthy grassland,HLD and MC of bean farmland all had significant positive effects on soil EOC content.The SPD and HLD of healthy grassland,HLD and MC of corn farmland,and SPD of bean farmland all had significant positive effects on the WSOC content of the soil.Except for HLD and MC in corn farmland and SPD in bean farmland,SPD,HLD and MC of other land use types all had significant positive effects on soil LFOC content.The interaction between the AMF community composition and the driving factors such as glomalin,together dominated the changes of soil organic carbon and its components.4.Total extracted glomalin?T-GRSP?and easy-to-extract glomalin?EE-GRSP?contents varied greatly between different land-use patterns and soil depth.This difference and change were related to the spatial distribution and heterogeneity of soil organic matter and soil nitrogen and phosphorus.The contents of T-GRSP and EE-GRSP were forest>moderately degraded grassland>healthy grassland>corn farmland>bean farmland,which was closely related to vegetation richness and soil nutrient content.The contents of T-GRSP and EE-GRSP of the five land use types all showed a decreasing trend with the increase of soil depth.Under the five types of land use,the contents of T-GRSP and EE-GRSP had extremely significant positive effects on TOC,POC,LFOC and HFOC.The contents of T-GRSP and EE-GRSP in moderately degraded grassland,corn farmland and bean farmland all had a positive effect on soil MBC content.The contents of T-GRSP and EE-GRSP in forest had a significant negative effect on soil MBC content.The contents of T-GRSP and EE-GRSP in healthy grassland and corn farmland had a significant positive effect on soil EOC content.The contents of T-GRSP and EE-GRSP in healthy grassland and bean farmland have a significant positive effect on the WSOC content of soil.The interaction between the AMF community composition and the driving factors such as glomalin,together dominated the changes of soil organic carbon and its components.Through investigation and research on 175 soil samples of five land use types in 0-100 cm soil layer,it was found that soil organic carbon and its components are widely distributed and have vertical profile distribution characteristics.The change trend decreased with the increase of soil depth;and the content difference between different land use types is significant.The contents of TOC,HFOC,LFOC and POC in each soil layer are shown as forest>two grasslands>two farmlands.The content of soil organic carbon and its components is significantly affected by physical properties such as vegetation type,soil nutrients,and soil aggregate structure.Under different land use types,the species diversity and their litter significantly affected the conversion of soil nutrients,which in turn affected the activity of soil AMF and other microorganisms,and affected AMF infection,sporulation,mycelium growth and mycorrhiza development.Microbial metabolism such as AMF in the soil is beneficial to the formation of soil organic carbon and its components,affecting the diversity and high concentration of organic carbon components in the soil.AMF mycelium can not only secrete various soil enzymes,but also can be used as an extension of fine roots,increase the surface area of the root system,assist the root system to absorb nutrients in the soil,and promote the process of soil metabolism.AMF infects plant roots and improves soil aggregates,which can increase the nitrogen and carbon content in the soil and improve the soil structure,thereby enhancing the carbon source metabolism of soil organic carbon by the soil microbial community,which can be used in a short time.Increase the content of organic carbon and its components in the soil around the root system.AMF,host plant and root environment constitute a balanced system,which are connected and influenced by each other.In the farmland soil,fertilization leads to the intervention of foreign nitrogen and phosphorus,which reduces the AMF colonization status and reduces the contribution of AMF to soil organic carbon and other nutrients.Soil organic carbon and its components are the core of soil quality,its stability can affect the growth of plants to a certain extent,its changes can affect global climate change by affecting CO₂ emissions,and it play a crucial role for soil structure formation and it can improve the soil nutrients status.There was a significant correlation between the AMF community structure of different land use types,the content of glomalin and the content of soil organic carbon as well as its components.This study has important theoretical value for understanding the impact of AMF on soil organic carbon composition and distribution under different land use types;by revealing the effect and mechanism of AMF on soil organic carbon composition and distribution characteristics under different land use types,and this study has important scientific significance to fully understand the role of microbes for the global carbon cycle dynamics.