Canopy processing of atmospheric dust creates a short-term phosphorus pathway in a tropical forest
Gross, A., T. E. Wood, J B.-W. Stuut and A. Lokshin. 2026.
Abstract
Phosphorus (P) availability constrains productivity in many humid tropical forests, where
highly weathered soils retain P in poorly available forms and external inputs are needed to
offset long-term losses. Caribbean forests receive new P through trans-Atlantic Saharan dust
and episodic African biomass-burning particles, however how this particulate P enters forest
nutrient cycling remains poorly understood. Here, we examined the fate and uptake of
particulate P in the Luquillo Experimental Forest, Puerto Rico, using a foliar dust-application
experiment and soil incubations with mineral dust and wildfire ash. In soils, both materials
increased P supply to ion-exchange membranes, but mineral dust-derived P was rapidly
transferred into Fe- and Al-associated pools, whereas wildfire ash generated greater short-term
P availability. On leaves, mineral dust exposure resulted in foliar uptake of dust-derived Fe and
P, with P uptake quantified using Fe as a conservative anchor. Particles recovered from leaf
surfaces contained more bicarbonate-extractable P than the applied dust, indicating that contact
with leaves increased the lability of P remaining in deposited particles. Together, these findings
identify two complementary canopy pathways: direct foliar uptake of dust-derived P and leaf surface processing that increases the fraction potentially available for subsequent uptake, either
from foliage or, following redistribution in throughfall, by roots. By revealing a pre-soil
pathway for atmospheric P, our results highlight a process not explicitly represented in most
terrestrial nutrient-cycle frameworks that may affect how models represent the biological
availability of dust-derived P and its coupling to tropical forest carbon cycling.
