Can soil phosphorus availability in tropical forest systems be increased by nitrogen-fixing leguminous trees?

Understanding the role of N-fixing leguminous trees for phosphorus (P) cycling in highly weathered tropical soils is relevant for the conservation of natural forests as well as the sustainable management of agroforests and forest plantations with low P input in the Brazilian Atlantic Forest region. We hypothesized that N-fixing leguminous trees can increase the availability of soil P by exploiting different P sources without causing a depletion of soil organic P due to efficient biogeochemical cycling, but empirical evidence remains scarce. For this purpose, P nuclear magnetic resonance spectroscopy (P NMR) was used for quantifying soil P forms and the Hedley sequential extraction to determine soil P fractions.