Impacts of biomass burning emissions and land use change on Amazonian atmospheric phosphorus cycling and deposition

Abstract

Phosphorus (P) availability constrains both carbon uptake and loss in some of the world's most productive ecosystems. In some of these regions, atmospheric aerosols appear to be an important, if not dominant, source of new P inputs. For example, previous work suggests that mineral aerosols from North Africa bring significant amounts of new phosphorus to the P-impoverished soils of the Amazon Basin. Here we use recent observations and atmospheric transport modeling to show that the Amazon Basin itself appears to be losing atmospheric phosphorus to neighboring regions as a consequence of biomass burning emissions, anthropogenic sources of mineral aerosols and primary biogenic particles. Observations suggest that biomass burning emissions and human disturbance are responsible for ∼23% of the phosphorus flux in the Amazon. Although biomass burning and disturbance may bring new phosphorus into nondisturbed regions, as a whole the Amazon appears to be losing phosphorus through the atmosphere. Phosphorus lost via atmospheric transport from the Amazon is deposited in the adjacent oceans and in other regions downwind. These results suggest that land use change within the Amazon may substantially increase phosphorus availability to the remaining undisturbed forests, and that this fertilization mechanism could potentially contribute to recent changes in carbon uptake measured in undisturbed stands, as well as fertilizing downwind ocean regions. Copyright 2005 by the American Geophysical Union.