Variability in potential to exploit different soil organic phosphorus compounds among tropical montane tree species

We hypothesized that tropical plant species with different mycorrhizal associations reduce competition for soil phosphorus (P) by specializing to exploit different soil organic P compounds. We assayed the activity of root/mycorrhizal phosphatase enzymes of four tree species with contrasting root symbiotic relationships–arbuscular mycorrhizal (angiosperm and conifer), ectomycorrhizal and non-mycorrhizal–collected from one of three soil sites within a montane tropical forest. We also measured growth and foliar P of these seedlings in an experiment with P provided exclusively as inorganic orthophosphate, a simple phosphomonoester (glucose phosphate), a phosphodiester (RNA), phytate (the sodium salt of myo-inositol hexakisphosphate), or a no-P control. The ectomycorrhizal tree species expressed twice the phosphomonoesterase activity as the arbuscular mycorrhizal tree species, but had similar phosphodiesterase activity. The non-mycorrhizal Proteaceae tree had markedly greater activity of bot...