1. The residence time of phosphorus (P) in trees is a consequence of plant adaptation to P deficiency, with longer P residence time on soils with low P availability. P residence time has been studied at the leaf or canopy level but seldom at the whole-tree level. Whereas P residence time at the leaf or canopy level is largely determined by leaf longevity and the resorption of P before leaf abscission, P residence time at the whole-tree level will also be influenced by differences in P allocation to different plant parts because leaves and woody organs have distinct longevities.

2. We estimated the residence time of P in aboveground tree biomass (AGB) as the ratio of P mass (i.e. leaves plus wood) to the annual flux of P via litterfall (i.e. fine litter plus coarse woody debris) for seven tropical rain forests with different soil P availabilities on Mount Kinabalu, Borneo. We analysed the effects of P allocation to and resorption from leaves on P residence time along a soil P gradient.

3. P residence time (2.7–9.8 years) was approximately one fifth of biomass residence time (AGB/annual litterfall mass; 19.8–48.8 years). This was due to a disproportionately greater relative allocation of P to leaves (P mass in leaves/P mass in AGB; 0.11–0.46), which had a smaller fraction of biomass (leaf biomass/AGB; 0.02–0.05) but a shorter longevity (1.0–1.8 years).

4. The relative allocation of P to leaves was often high on low-P soils, and P residence time was expected to be short. By contrast, the resorption rate of P from leaves was also high on low-P soils, which extended P residence time with P deficiency. Consequently, P residence time was nearly constant across the forests.

5. The short residence time of P relative to biomass indicates that P residence time depends largely on relative P allocation among plant organs. Similar P residence times among sites were maintained because greater P allocation to leaves on low-P soils was effectively offset by higher P-resorption efficiency.