Stream acidification and base cation losses with grassland afforestation

Abstract

To investigate the biogeochemical and hydrological consequences of land use change, stream water was sampled in paired watersheds in Uruguay and Argentina. Where both pines and eucalypts were planted nearby, eucalyptus showed a stronger acidifying effect than pine. At test sites, Ca, Mg, and Na concentrations were >30% lower in afforested soils than in grassland soils, and pH was significantly lower below 10 cm depth. Stream measurements taken over three years illustrate that these soil changes were also manifested in stream water chemistry. The data suggests that repeated harvesting could negatively impact the soil store of base cations and reduce downstream water quality.