Growth of mature beech in relation to ozone and nitrogen deposition: An epidemiological approach

Stem increment of mature Fagus sylvatica L. from 57 plots in Switzerland wa s analysed with respect to environmental factors using multilinear regressi on. Nitrogen (N) deposition was positively correlated with stem growth, wit h an increase by 41.8% (confidence interval 38.9-44.2) per 10 kg N ha(-1) a (-1). There was a negative relationship between ozone (O-3) dose and diamet er increment. The fit was better for maximum rather than average exposure v alues. Coefficients indicated growth changes of -22.5% (14.3-28.6 confidenc e interval) and -35.1% (17.8-47.3) respectively per 10 ppm hours. These cha nges exceed the -6.1% found in experiments with beech seedlings. This diffe rence is mainly attributed to the fact that the seedling data are calculate d for a single season's exposure whereas the stem increment data extend ove r four years, representing the product of four annual reductions. Increased sensitivity of mature trees compared to seedlings, however, is also sugges ted.