Atmospheric deposition and ionic interactions within a beech canopy in the Karkonosze Mountains

A method of artificial foliage placed above rain collectors, which enables to estimate total atmospheric inputs of elements, was employed to study processes related to ionic flow through a tree canopy. The investigations were conducted within a beech forest in the Karkonosze Mountains, in 1996–1997. An analysis of net canopy exchange (throughfall flux–atmospheric input) revealed that NH4+, NO3−, H+ had been retained in the canopy, Ca2+, Na+, Cl−, SO42−, PO43− flowed passively, whereas K+ and Mg2+ had been removed from the tree foliage. Ammonium absorption was more efficient than that of NO3− ions, because NH4+ was taken up from rain-waters and aerosol–gaseous fraction of the atmospheric input, whereas NO3− ions were captured primarily from the latter source. Retention of H+ was also related exclusively to the aerosol–gaseous input. Leaching losses of K+ and Mg2+ did not result from exchange reactions of these ions with retained H+, but from ionic exchange between NH4+ and K++Mg2+. At the same time, neutralisation of H+ in the canopy has been attributed to NO3− absorption, resulting most likely from HNO3 vapour penetration into the plants.