Atmospheric nitrogen deposition affects forest plant and soil system carbon:nitrogen:phosphorus stoichiometric flexibility:A meta-analysisOACSTPCD

Background:Nitrogen(N)deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant uptake.However,the effect of N deposition on the flexibility of carbon(C),N,and phosphorus(P)in forest plant-soil-microbe systems remains unclear. Methods:We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant,soil and microbial biomass C,N and P nutrients and stoichiometry to N addition in different N intensity(0-50,50-100,＞100 kg·ha-1.year-1 of N),duration(0-5,＞5 year),method(understory,canopy),and matter(ammonium N,nitrate N,organic N,mixed N). Results:N addition significantly increased plant N∶P(leaf:14.98％,root:13.29％),plant C∶P(leaf:6.8％,root:25.44％),soil N∶P(13.94％),soil C∶P(10.86％),microbial biomass N∶P(23.58％),microbial biomass C∶P(12.62％),but reduced plant C∶N(leaf:6.49％,root:9.02％).Furthermore,plant C∶N∶P stoichiometry changed significantly under short-term N inputs,while soil and microorganisms changed drastically under high N addition.Canopy N addition primarily affected plant C∶N∶P stoichiometry through altering plant N content,while understory N inputs altered more by influencing soil C and P content.Organic N significantly influenced plant and soil C∶N and C∶P,while ammonia N changed plant N∶P.Plant C∶P and soil C∶N were strongly correlated with mean annual pre-cipitation(MAT),and the C∶N∶P stoichiometric flexibility in soil and plant under N addition connected with soil depth.Besides,N addition decoupled the correlations between soil microorganisms and the plant. Conclusions:N addition significantly increased the C∶P and N∶P in soil,plant,and microbial biomass,reducing plant C∶N,and aggravated forest P limitations.Significantly,these impacts were contingent on climate types,soil layers,and N input forms.The findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.