Relationships between crown condition of beech (Fagus sylvatica L.) and throughfall chemistry

A two-step regression procedure was used to predict the impact of throughfa ll chemistry on the defoliation of Fagus sylvatica L. over a 10-year-monito ring period at three plots in northern Belgium. The impact of throughfall c hemistry on crown condition was examined after accounting for influences of site, stand, climate and diseases. In a first step, defoliation was regres sed on site, stand, climate and disease parameters. The residual defoliatio n of this standard set was correlated with 27 throughfall variables. Climatic variables of the year preceding the year of crown assessment accou nted for 79% of the variation in current defoliation. Site, stand and disea se factors were not included and were still part of the residual defoliatio n. The study of the residual defoliation revealed that high throughfall dep ositions of sulphate and ammonium and high throughfall ratios of SO4/Mg enh anced defoliation.