The Soil Priming Effect In Forest Successions And The Underling Mechanism

Soil carbon accumulation is mainly regulated by plant litter input and microbial carbon decomposition during forest succession.Plant litter input would cause the priming effect,which could increase decomposition rate of soil organic carbon by up to 4 times and is a key process in influencing soil carbon dynamic.However,it is still unclear about soil priming effect during forest successions and its influencing factors(e.g.,soil properties and microbes).In this study,we first conducted a ¹³C-labeled glucose addition experiment to explore the changes in soil priming effect and its regulatory factors during forest succession in Tiantong ecological station.Meanwhile,we explored the changes in soil priming effect along forest successions under different climatic conditions in combination with the data from Changbai and Dinghu ecological station forest successional sequences.The main findings are as follows:(1)Soil priming effect increased significantly along forest successional stages in Tiantong ecological station.Relative soil priming effect was 11.79%at the late-successional stage,which was significantly higher than that at early stage(4.11%)and middle stage(5.14%).Soil total dissolvable nitrogen(TDN)and soil C:N ratio(TC:TN)were the important abiotic factors in influencing soil priming effect.TDN was positively correlated and TC:TN was negatively with soil priming effect.MBN,MBC:MBN,fungal?diversity,and relative abundance of Basidiomycota,Rozellomycot and Myxococcota were the important biotic factors in influencing the priming effect.Among them,MBC:MBN was negatively correlated and the other factors were positively with soil priming effect.Along the different forest successional stages in Tiantong ecogical station,soil microbes explained 47.47%for the variation of soil priming effect,which was significantly higher than soil properties(28.08%).(2)Changes in soil priming effect along forest successions were different in Changbai,Dinghu and Tiantong ecological stations with different climatic backgrounds.In Changbai ecological statation,soil priming effect gradually decreased during the forest succession(P<0.05),but it had no significant difference at different forest successional stages in Dinghu ecological station.Among soil properties,NH₄⁺-N was the most important factor in influencing soil priming effects with a significant positive relationship,while NO₃^--N and TN were negatively correlated with soil priming effect under different climatic backgrounds.Among the biotic factors,relative abundances of Mortierellomycota,Mucoromycota,Proteobacteria,Verrucomicrobiota,and Planctomycetota were the key microbial phyla that impacted soil priming effect under different climatic backgrounds,which were significantly positively correlated with soil priming effect except Verrucomicrobiota with a negative correlation.In addition,latitude and forest age were also the important factors regulating soil priming effect under different climatic backgrounds.The joint climate,soil properties,and microbes are more important(40.18%)than independent soil properties(14.82%)and microbes(18.88%)in explaining the variation of soil priming effect along forest successions under different climatic backgrounds.In conclusion,forest succession is an important factor influencing soil priming effect with considerable differences in the patterns of soil priming effect along forest successional stages under different climatic backgrounds.In temperate forests with high latitude,soil priming effect decreased along forest succession.In the southern subtropical forests with low latitude,soil priming effect was no significant different or increased during forest succession.In Tiantong ecological station,soil microbes had the highest explanation for the variation of soil priming effect at different successional stages.While under different climate backgrounds,the joint explanation of climate,soil properties and microbes was the highest for the variation of soil priming effect.Our results will deepen the understanding of soil carbon processes along forest succession,and provide data support and theoretical basis for the estimation of forest carbon sink capacity and potential in the context of global change.