Comparison of Cation Leaching in Five Northern Hardwood Stands Along an Air Pollution Gradient Using a Throughfall Modeling Approach

1990

S. 295-306

3 Tab., 15 Lit. Ang.

Unselbständiges Werk

200085628

Five northern hardwood sites were established along a wet sulfate deposition gradient in the Great Lakes Region of the United States. Stand and soil characteristics of the sites were similar. Precipitation and throughfall was collected weekly at each site during the growing season of 1988. Canopy exchange rates of Ca2+, K+, and Mg2+ were determined for each site by fitting a net deposition model to the precipitation and throughfall chemical fluxes measured during the study period. An approximate two and eight fold increase along the gradient in volume weighted precipitation concentrations of SO4 2- and H+ respectively were evident during the study period. Foliar leaching of K+ and Ca2+ was positively related to concentrations of H+ in precipitation. No significant differences in canopy exchange rates of Mg2+ were found among the sites. Canopy exchange rates of K+ appeared to be more sensitive to changes in precipitation acidity than were Ca2+ exchange rates.