Phosphorus acquisition and canopy dominance in tropical and subtropical forests: response to Brearley et al.

Brearley et al. [1] comment on our opinion paper concerning a proposed ‘virtual phosphorus acquisition’ (VPA) hypothesis, which puts forward the idea that dominance of canopies in (mainly) Asian forests is driven by the superior ability of ectomycorrhizal (ECM) fungi to acquire phosphorus from diverse chemical forms, produce more extensive and functionally important hyphal networks, and provide resistance against root pathogens, compared with arbuscular mycorrhizal (AM) fungi [2]. These belowground activities require energy, and dominance of the canopy provides the capacity of hosts to allocate large amounts of carbon to ECM fungi. While the VPA hypothesis was not intended to be a universal explanation of canopy dominance, we suggest that it provides a parsimonious view of the evidence on the subject thus far and disagree that it is an oversimplification. That said, as with any synthesis of complex systems, there will be cases where the VPA hypothesis does not fit, and Brearley et al. [1] speculate on some cases where this may be the case, and we encourage others to do the same.