Statistical Analyses
Whole plot average plant biomass, foliar P concentration and N:P ratio were calculated using a weighting factor for each species, which was estimated by determining the average basal diameter of each species from 2013 to 2019. Foliar N concentrations were originally presented in Lie et al., (2021). Plant P uptake was estimated by the weighted sum of P accumulated by the four species (data from Wu et al., 2020). Plant P resorption efficiency was calculated as (1 – Pl/Pf × MLCF) × 100%, where Pl is litter P concentrations and Pf is the weighted foliar P concentrations of the four species; MLCF is the mass loss correction factor, which is 0.78 for evergreen broad-leaved forest tree species (Vergutz et al., 2012).
Differences in P status in plant, soil and leachate, as well as soil phosphatase activity and soil Fe minerals under treatment were analyzed using linear mixed-effects model. Warming treatment and experimental time were treated as fixed factors, while plot was treated as a random factor. Pairwise comparisons of means were tested by Least Significant Difference test. Data were transformed to meet the assumptions of normality and homogeneity of variances when necessary. Statistical significance was defined as P <  0.05. Linear mixed models were performed by “lmer” function in “lme4” package (Bates et al., 2015) using R version 3.6.1.