Lichens as Bioindicators of Air Quality
Hauck, Markus .
Ecology of epiphytic lichens in northern coniferous forests under different levels of air pollution.
CIRCUMPOLAR boreal and oroboreal coniferous forests form the world's largest forest type. Because of their cool and often also humid climate they are important habitats of epiphytic lichens. Significant progress has been made recently at analyzing site factors that control epiphytic lichen diversity within northern conifer forests. Microclimate and habitat continuity are long since known as relevant parameters. Here, results of case studies in montane coniferous forests of central Europe, north-eastern Asia as well as western and eastern North America are presented that try to elucidate the significance of chemical site factors in forests exposed to different levels of air pollution.
At sites with heavy atmospheric pollutant load, the abundance of many lichens is limited by high concentrations of inorganic sulphur, acidity, and heavy metals in stemflow and bark. Because of the higher intercepting surface, epiphytic lichen growth is more severely inhibited by pollutants deriving from atmospheric deposition on healthy trees than on conifers that are dead or show heavy needle loss. This explains why epiphytic lichen distribution is more different between living trees and snags in polluted than in remote areas.
With decreasing pollutant load, other site factors gain in importance. Aside from microclimate and stand age, these factors include natural chemical (edaphic) parameters, the significance of which has been widely neglected, so far. A key factor in this context is the Mn availability from the soil, as conifers readily take up Mn through their root system because of its role as a micronutrient, but deposit surplus Mn in their bark. These deposits affect epiphytes growing on the bark surface directly or when leached by precipitation. Decreasing lichen abundance with increasing Mn availability has been established in conifer stands of Eurasia and North America. Causality of correlations is suggested by experimental work including short-term laboratory and long-term transplant experiments.
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Projects and publications by Markus Hauck and group members
1 - University of Goettingen, Albrecht von Haller Institute of Plant Sciences, Untere Karspuele 2, Goettingen, 37073, Germany
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, August 1st, 2006
Time: 10:15 AM