Losses of Polyol through Leaching in Subarctic Lichens.

Upon rewetting, lichens lose polyols through leaching. We quantified leaching losses for 21 species under simulated rainfall. Polyol concentrations in these lichens range from 1.0 to 8.8%, with a mean of 2.8%. Leaching losses range up to about 7.5 mg (polyol)/g (lichen dry weight) in a typical rain event. The rate of polyol leaching declines exponentially, becoming negligible within 1 hour of continuous rain. The response of polyol leaching rate to rainfall intensity and amount varies between species-six species showed no response, one had increased leaching with increased rainfall intensity, four had increased leaching with increased amount of rainfall, and one had decreased leaching with increased total amount of rainfall. Polyol leaching rates are positively correlated with polyol concentration for 20 species. Literature values of average daily growth rates for subarctic lichens are of the same order of magnitude as leaching rates, suggesting that polyol leaching is an important part of the carbon budget of lichens.