Experiments and Observations on Epiphytic Lichens as Early Warning Sentinels of Forest Decline : Biologic Markers of Air-Pollution Stress and Damage in Forests. Workshop Papers

1989

S. 205-216

13 Abb., 2 Tab., 12 Lit. Ang.

Unselbständiges Werk

200069328

Forest declines are now widely reported in Europe and eastern North America, especially in high elevation areas where fogs, oxidants and SO2 frequently co-occur. Analyses of cloudwater indicate that high-altitude fogs are more acidic (Formel) than abient precipitation at the same sites and may be present for up to 50 % of the year. A cominbation of high humidity and nutrient enrichment normally allows for a prolific, species-rich apiphytic lichen flora on coniferous trees in the transition zones. In previous field studies, we have shown that boreal forest-floor lichens such as Cladina rangiferina respond to seasonal sprays of simulated, acidic rain of less than pH 3.5 by producing abnormal morphological and cytological strucutres. We have, therefore, selected a number of high-altitude sites showing varying degrees of forest dieback in Quebec, Vermont and New York (North America) and in the Black Forest and Hartz Mountains (Germany) to determine whether similar abnormalities occur in lichen populations exposed to ambient levels of acidity. We shall discuss the sui- tability of two, widely-distributed epiphytic lichens, Hypogymnia physodes and Pseudevernia sp., as early warning indicators of forest dieback, based on a comination of morphological, cytoplasmic and chemical data.