Soil Microbial Diversity And Stoichiometric Dynamics In Boreal Forests At Different Successional Stages

Clarifying the response of soil microbial communities and their potential functions to the succession is of great significance for understanding the biogeochemical processes of soil microorganisms participation and the sustainability of forest development.At present,the study of microbial community dynamics during the process of succession remains poorly understood in boreal forest ecosystems.In addition,the stoichiometric imbalance between microbes and their resources determines the element limitation of microbes,which will change their carbon and nutrient utilization efficiency,and ultimately affect the biogeochemical cycle driven by soil microbes.Thus,in order to study the dynamics of microbial diversity caused by succession,we adopted the "space instead of time" method and selected four habitats in a national natural reserve(including grassland,birch forest,mixed forest and larch forest)to represent the primary succession sequence of the boreal forest.We used 16 S and ITS r RNA gene sequencing to detect bacterial and fungal communities and used FAPROTAX and FUNGuild database to predict bacterial and fungal functional groups.The results showed that forest succession significantly changed the community composition of bacteria and fungi,among which the fungal community was more sensitive to the changes of forest succession stage.The relative abundance of ectomycorrhizal fungi significantly increased with the succession,while the relative abundance of the bacterial functional groups involved in the nitrogen cycle did not change significantly,indicating that fungi might play a major regulatory role in the nutrient cycling process during the succession process.In this study,the soil total carbon and total nitrogen were the dominating factors affecting the soil microbial community and the structure of fungal functional groups.Bacteria were more responsive to total nitrogen.Our results suggested that the transformation of fungal community structure and functional groups may play a vital role in soil nutrient cycling during boreal ecosystems succession.The succession of boreal forests resulted in a stoichiometric imbalance between soil microorganisms and their resources,which will lead to changes in the limit of microbial elements.In particular,the C: N imbalance increased significantly with succession,which means that the nitrogen limitation of microorganisms increases in the later stage of succession.Studies on the stoichiometric homeostasis of microorganisms showed that soil microorganisms still maintain relative homeostasis even though the stoichiometric imbalance is changed by boreal forest succession.In addition,the metabolic entropy(qCO₂)of microorganisms increased significantly with the development of succession,which indicates that the carbon use efficiency of microorganisms decreases with the development of succession.At the same time,the metabolic entropy of microorganisms was positively correlated with soil C:N and C:N imbalances.These results indicated that the adaptation mechanism of microorganisms to stoichiometric imbalances can anticipate microbial metabolism and nutrient cycling processes.In general,this article explored the adaptation strategies of microbial communities to environmental changes during the succession of boreal forests and the functional feedback of microbes through the study of the diversity of microbial communities.Secondly,we applied the theory of ecological stoichiometry to further understand the soil ecological processes involved by microorganisms.Through the above research,this article provided certain data and theoretical references for understanding the relationship between microbial community,function and succession in the long-term succession of boreal forests.