Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
CARBON-WATER-NITROGEN RELATIONSHIPS BETWEEN LICHENS
AND THE ATMOSPHERE: TOOLS TO UNDERSTAND METABOLISM
AND ECOSYSTEM CHANGE
Máguas C.
Centre for Environmental Biology, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
Lichens are highly diverse organisms offering a number of particular physiological and morphological
characteristics, which enable the assessment of several environmental and ecological factors. Since
lichens grow slowly and are strongly influenced by microclimatic conditions such as light, water,
temperature, CO 2 concentration, and airborne deposition elements (i.e. nitrogen), their organic material
(OM) integrates the interactions between local atmosphere conditions at their specific microhabitat
over a long period. Moreover, this OM is also modeled by the continuous “equilibrium” behavior of
lichens towards the surrounding atmosphere which is strong influenced by several thallus traits such as
morphology, carbon source and sink (which are mainly influenced by photosynthesis and respiration),
water sources and availability time periods and nitrogen bio-availability. Indeed, our current knowledge
in “biosphere-atmosphere exchange processes” lacks the understanding of these complex interactions
between lichen biogenic fluxes of carbon, water and nitrogen and atmosphere. For that, tools such
the application of stable isotope techniques, may provide new insights into understanding lichen
physiological and ecological processes. Due to their direct dependency on environmental conditions,
lichens’ stable isotope compositions reflect changes of carbon and water as an integral over a long
period and on a microenvironmental scale. Their poikilohydric nature enables them to settle under
environmental conditions where higher plants are unable to survive and also to assimilate extraordinary
substrates such as vapor or carbon microresources which are not commonly utilized by higher plants.
Another important aspect is the need of a general framework in order to use lichen communities to
evaluate and monitor complex ecosystems responses in a changing environment. Although there is an
obvious local spatial scale of influence in what concerns environmental factors, which may limit the use
of lichen communities to study factors associated to global change at a planetary scale, the application
of spatial explicit analysis can contribute to model lichen responses to global drivers such as climate
or eutrophication. The main objective of this talk is to provide an overview of past and recent insights
on the interactions between local atmosphere and lichen-metabolism and functional diversity in order
to a better use of lichens as tracers for biosphere-atmosphere exchange processes, and early impact
indicators of global change.
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