Mycorrhizal phosphorus efficiencies and microbial competition drive root P uptake

Phosphorus (P) availability shows large differences among different soil types, affecting P nutrition of forest trees. Chemical binding of P to soil moieties affects partitioning of P between soil particles and solution, affecting soluble P concentrations upon which plants, their associated mycorrhizal symbionts, and microbes feed. The goal of this study was to characterize root P uptake by mycorrhizal and non-mycorrhizal root tips in competition with microbes in situ in the organic and mineral layer of a P-rich and a P-poor forest. We used intact soil cores (0.2m depth) from beech (Fagus sylvatica) forests to tracing the fate of 33P in soil, plant and microbial fractions. We used the dilution of 33P in the rhizosphere of each soil layer to estimate the enrichment with new P in mycorrhizal and non-mycorrhizal root tips and root P uptake. In soil cores from P-rich conditions, 25% and 75% of root P uptake occurred in the organic and mineral layer, respectively, whereas in the P-poor fores...