Stand biomass, productivity and their stability
The biomass of each (sub)plot, from 400 to 2500 m2, was calculated by summing the total biomass (stem + branches + foliage + roots) for each tree, which was estimated using the allometric equations that were separately developed for each forest type (Table S1). Annual biomass increment was calculated as the difference in stand biomass between two adjacent years (△B = Bt - Bt-1, where Bt is the stand biomass of the current year). Noted that △B does not include litterfall production and thus is a part of net primary productivity, however, for simplicity in narration we abbreviated it as productivity hereafter.
To analyze the relationship between diversity and ecosystem functions, we calculated the multi-year mean biomass (2004-2010) and productivity (2005-2010) for each plot (subplot). To explore the effect of diversity on ecosystem stability, we calculated the temporal stability index (Tilman et al. 2006; van der Plas 2019) based on the annual biomass and productivity data for each (sub)plot. Temporal stability is a measure of how community productivity (biomass) fluctuates around its multi-year means: S = 1 / CV = υ/б, where υ is the mean value for a time period andб is the standard deviation over the same interval, while CV is the coefficient of variation (Tilman et al. 2006; van der Plas 2019). Hereafter, the stability of biomass and productivity are abbreviated as S_B, S_P, respectively.