Partitioning of soil phosphorus among arbuscular and ectomycorrhizal trees in tropical and subtropical forests

Partitioning of soil phosphorus (P) pools has been proposed as a
key mechanism maintaining plant diversity, but experimental support is lacking.
Here, we provided different chemical forms of P to 15 tree species with
contrasting root symbiotic relationships to investigate plant P acquisition in
both tropical and subtropical forests. Both ectomycorrhizal (ECM) and
arbuscular mycorrhizal (AM) trees responded positively to addition of inorganic
P, but strikingly, ECM trees acquired more P from a complex organic form
(phytic acid). Most ECM tree species and all AM tree species also showed some
capacity to take up simple organic P (monophosphate). Mycorrhizal
colonization was negatively correlated with soil extractable
P concentration, suggesting that mycorrhizal fungi may regulate organic P acquisition
among tree species. Our results support the hypothesis that ECM and AM plants partition
soil P sources, which may play an ecologically important role in promoting species
coexistence in tropical and subtropical forests.