Response of soil microbial biomass carbon and nitrogen to vegetation succession in different soil depths of karst fault basin

YAN Jiahui; QIU Jiangmei; LI Qiang

doi:10.11932/karst20230519

Abstract：The karst fault basin in Yunnan Province is a typical ecological fragile area in Southwest China,and it is characterized by dramatic topographic changes,coexistence of faulted basins,basins and mountains,and seasonal drought and water shortage,so surface water erosion likely occurs.Soil microorganism promotes the circulation of nutrient elements in soil,among which microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)—the indicators of soil quality—are of great research significance.In this study,primitive forests,grasslands,artificial forests,shrubs and corn fields in the karst fault basin of Yunnan were selected as the study objects.The changes of MBC and MBN in soil were measured,and then their response to vegetation types was analyzed. The results showed that the contents of soil MBC and MBN in shrubs were the highest,indicating that the shrubs in this study area are more conducive to the accumulation of soil MBC and MBN.In contrast,the contents of soil MBC and MBN in primary forests were lower than those in shrubs,which was considered to be the result of the the decrease of effective nutrients available for vegetation growth due to the degradation of primary forests,or the intense competition between plant growth and microorganisms for nutrients in primary forests and the fact that the demand capacity of vegetation growth was greater than the conversion capacity of soil microorganisms.The study also found that the contents of MBC and MBN increased at first and then decreased with vegetation succession,which may be related to the organic matter content and oxygen availability as well as the surface layer that conforms to microbial growth conditions.The content of soil MBC decreased with the increase of soil depth.Moreover,the soil depth and vegetation type are the significant influencing factors of the content of soil MBC(P＜0.05),and the soil depth was the most significant factor(PP＜0.01).These findings provide a theoretical basis for the control of soil erosion and rocky desertification in karst fault basin of Yunnan Province.