3) Functional diversity
Previous studies have shown that maximum tree height and wood density
were key functional traits to predict forest biomass and productivity
(Ruiz-Benito et al. 2014; Woodall et al. 2014; Wu et
al. 2015b). Consequently, we calculate functional diversity based on
these two traits. The maximum tree height data for each species was
obtained from the ”Flora of China” (Editorial Committee of Flora of
China, 2004). The wood density data were retrieved from the global wood
density database
(http://datadryad.org/repo/handle/10255/dryad.235)
and China Woody Plant Wood Density Database (Zhang et al. 2011).
To represent the three diversity components, we calculated functional
richness (FRic), functional evenness (FEve), and functional divergence
(FDiv) for each (sub)plot. FRic is the amount of niche space filled by
species in the community, while FEve is the evenness of abundance
distribution in filled niche space, and FDiv is the degree to which
abundance distribution in niche space maximizes divergence in functional
characters within the community (Mason et al. 2005). All
functional diversity indices were calculated with the R package “FD”
(Laliberté & Legendre 2010).