Time since fire affects ecological stoichiometry of plant-soil-microbial systems of Betula platyphylla, a pioneer species in burnt areas of China’s boreal forest

Plant stoichiometry and nutrient allocation may reflect adaptation strategies to environmental nutrient changes.Fire,as a major disturbance in forests,mediates soil nutrient availability that may influence plant nutrient dynamics.However,plant–soil stoichiometric allocation strategies during different post-fire periods and the effects of soil,enzymes,and microbial biomass on plant stoichiom-etry are largely unknown.The pioneer tree species Betula platyphylla in burnt forests of northern China was the object of this study,and severely burned areas selected with dif-ferent fire years.Nearby unburned areas acted as a control.Carbon(C),nitrogen(N),and phosphorus(P)contents in leaves,branches,and fine roots and rhizosphere soil,C-,N-and P-acquiring enzyme activities were examined.Microbial biomass C,N,and P were measured,and factors influenc-ing C:N:P stoichiometry of plants during the burned area restoration were explored.Our results show that C and N contents in leaves increased with time since fire,while C and P in branches and C,N and P in fine roots decreased.Activities of C-,N-,and P-acquiring enzymes and microbial biomass N increased with time since fire.Redundancy analy-sis showed that changes in soil N-acquiring enzyme activity,microbial biomass C,and N had significant effects on plant ecological stoichiometry.These results show a significant flexibility in plant nutrient element allocation strategies and C:N:P stoichiometric characteristics.Soil extracellular enzyme activity drives the changes in stoichiometry during the process of post-fire restoration.