Forest floor contribution to phosphorus nutrition: experimental data

• Although accumulation of decomposing litter temporarily removes nutrients from active circulation, it creates a medium that is more suitable for nutrient uptake where soil conditions are unfavorable. • A pot experiment was conducted using labeling of isotopically exchangeable phosphate ions of the soil and applying the dilution principle to accurately assess the contribution of the forest floor to P nutrition of maritime pine seedlings (Pinus pinaster Ait.). Three-week-old maritime pine seedlings were planted in pots containing either mineral soil (MS) or mineral soil covered with a forest floor layer (MS+FF). • After 130 d, P uptake was still insignificant in the MS treatment while the P content of the seedlings in the MS+FF treatment increased tenfold with respect to the initial P content. In the latter treatment, the forest floor contributed 99.1% of the P supply to pine seedlings. • The higher P uptake from the forest floor than from the mineral soil may be explained by its lower ability to retain inorganic P, which enabled a higher concentration of inorganic P to be maintained in solution.