Seasonal variation in throughfall and stemflow chemistry beneath a European beech (<i>Fagus sylvatica</i>) tree in relation to canopy phenology

Abstract

The effect of canopy phenology on major ion fluxes beneath a mature European beech ( Fagus sylvatica L.) tree is examined. Annual and seasonal ion fluxes to the forest floor were significantly higher than the incoming wet-only deposition for all ions measured other than H + . The annual throughfall to wet deposition ratio generally ranged from 2.1 to 4.8. Stemflow contributed 9%–19% of the ion input to the forest floor, except for H + . Throughfall enrichment of K + , Ca 2+ , Mg 2+ , and NO 3 – was significantly higher in the leafed than in the leafless season, in contrast to Na + , NH 4 + , and H + . The temporal pattern of ion enrichment indicated canopy release of K + , Ca 2+ , and Mg 2+ throughout the leafed season, of Na + , Cl – , and NH 4 + from emerging leaves, and of Cl – and SO 4 2– from senescing leaves. The contribution of canopy leaching to annual net throughfall and stemflow was estimated at 96% (K + ), 54% (Ca 2+ ), 40% (Mg 2+ ), 12% (Cl – ), and 7% (Na + , SO 4 2– ). Dry deposition accounted for 58%–75% of the total deposition onto the canopy. The throughfall enrichment during the leafless season indicated high particulate and gaseous dry deposition onto the woody canopy as well as K + release from European beech branches.