DIVERSITY AND INDICATOR VALUES OF EPIPHYT IC LICHENS OF THE MOST COMMON TREE SPECIES - A METHODOLOGICAL APPROACH TO THE ASSESSMENT OF ENVIRONMENTAL-CHANGES IN FOREST AND NON-FOREST AREAS

On 132 long-term ecological observation plots in the Swiss Central Pla teau and the Pre-Alps the epiphytic lichen flora of 849 trees was surv eyed by standard sampling. The lichen data of all tree species in fore st and non-forest areas were analysed in order to provide simple, repr oducable and comparable characteristics for long-term observation. For the 10 most common tree species in forest and non-forest areas the me an number of lichen species, the mean cover of lichens and bryophytes, as well as the mean indicator values for light, reaction and toxitole rance (Wirth 1992) were determined. Based on the data of Picea abies i n forest, arranged in groups according to the 4 vegetation belts and 5 dbh-classes, the mean values and their confidence intervals were calc ulated for qualitative and quantitative (cover) data. For the detectio n of environmental changes, ordinal weightening of cover-estimates is proposed, considering effort, reproducibility and accuracy of sampling and calculation. As the indicator values are ordinal scaled from 1 to 9, and their distribution on the scale is not symmetric, the calculat ion of their mean values is not unproblematic. The effect of the latte r was estimated by comparison with calculations based on a scale from 1 to 5 with a symmetric distribution of all indicator values. Finally, for the 5 most abundant tree species in forest and non-forest areas, the estimates and their confidence intervals of each of five indicator -classes were calculated. If sample size is big enough, estimates of i ndicator-classes, especially for toxitolerance, are proposed for ecolo gical long-term characterisation. The ecological indicator values of W irth (1992) have shown to be an appropriate tool for long-term observa tion. In this study 79% of the most abundant species are characterized by indicator values. 12 trees were without any indicator-lichen, only 2 more than with no lichens at all.