LICHEN WATER RELATIONS UNDER DRYING CONDITIONS

The loss of water by evaporation in various species of lichens has been examined under a range of controlled windspeed/radiation regimes. Temperate and arctic species both show a type of morphological control of evaporation. Such control varies, however, with the nature of the surrounding environment. Evaporation from those species which show a very low resistance to evaporative water loss such as Bryoria nitidula, Umbilicaria deusta and U. veiled appears to be relatively insensitive to increases in radiant flux. Conversely those species, or specific growth forms, which show a high resistance to evaporative water loss, such as Cladina stellaris and U. muhlenbergii, appear to be sensitive to increases in supply of radiant energy. These results suggest that the morphological control of evaporation in lichens is significant to the ecology of this group of plants.