We used the Shannon-Wiener biodiversity index (Eq. (2)) to quantify
tree species diversity within each plot (Magurran, 2004). We used
relative basal area, instead of relative abundance, to weight the number
of tree species within each plot, because basal area reflects relative biomass
and hence better indicator of plant performance than relative
abundance (Ali et al., 2016b; Zhang and Chen, 2015).