|Langusch, J; Borken, W; Armbruster, M; Dise, NB; Matzner, E: Canopy leaching of cations in Central European forest ecosystems - a regional assessment, Journal of Plant Nutr. Soil Sci., 166, 168-174 (2003)|
The leaching of Ca, Mg and K from canopies is a major pathway of these cations into forest soils. Our aim was to quantify rates of canopy leaching and to identify driving factors at the regional scale using annual fluxes of bulk precipitation and throughfall from 37 coniferous and deciduous forests of North and Central Europe. Total deposition of Ca, Mg, K and H+ was estimated with Na as an index cation. The median canopy leaching increased in the order: Mg (0.11 kmolc ha-1 a-1) < Ca (0.31 kmolc ha-1 a-1) < K (0.39 kmolc ha-1 a-1). Canopy leaching of Ca and K were positively correlated with the calculated total H+ deposition and H+ buffered in the canopy, whereas canopy leaching of Mg was not. With contrasting effects, fluxes of SO4-S and NH4-N in throughfall explained to 64% (P<0.001) of the Ca canopy leaching. Fluxes of NH4-N and Ca were negatively correlated, suggesting that buffering of H+ by NH3 deposition reduced canopy leaching of Ca. Amount of bulk precipitation and SO4-S in throughfall were identified as much weaker driving factors for canopy leaching of K (r2=0.28, P<0.01). Our results show that Ca is the dominant cation in buffering the H+ input in the canopy. At the regional and annual scale, canopy leaching of Mg appears to be unaffected by H+ deposition and H+ buffering in the canopy.