Undergrowth as a biomonitor for deposition of nitrogen and acidity in pineforest

The possible use of the understorey vegetation as a biomonitor for atmosphe ric deposition of acid and nutrients was explored by analyzing the vegetati on of two pine forest stands in central and northern Sweden. Percentage cov er of vascular plants, bryophytes and lichens was estimated in four factori al experiments with a total of 122 plots. In these experiments N, P, K, lim e and sulphuric acid had been regularly added over a period of ca. 15 years . Redundancy analysis (RDA) was used to detect treatment effects on the com position of the vegetation, and was compared to analysis of variance (ANOVA ) on Ellenberg's indicator values. Of all treatments nitrogen addition had by far the strongest effect, causing a shift in dominance from cryptogams a nd Ericaceae towards Deschampsia flexuosa and ruderal species. Acidificatio n caused a decrease in the cover of most species, while liming increased th e dominance of Ericaceae. There was a fairly good correspondence among the N fertilization, acidification and Liming treatments and the indicator scor es for nitrogen and acidity. Although the indicator method was not as sensi tive as RDA in discriminating between the treatments, it may have a wider a pplicability in biomonitoring because it yields information on possible cau sal factors behind differences in vegetation. (C) 1999 Elsevier Science B.V . All rights reserved.