Morphological traits in hair lichens affect their water storage

The aim with this study was to develop a method to estimate total area of hair lichens and to compare morphological traits and water storage in them. Hair lichens are an important component of the epiphytic flora in boreal forests. Their growth is primarily regulated by available water, and light when hydrated. Lichens have no active mechanism to regulate their water content and their water holding capacity (WHC, mg H2O/cm2) is thus an important factor for how long they remain wet and metabolically active. In this study, the water uptake and loss in five hair lichens (Alectoria sarmentosa, three Bryoria spp. and Usnea dasypoga) were compared. Their area were estimated by combining photography, scanning and a computer programme that estimates the area of objects. Total area overlap of individual branches was calculated for each species, to estimate total area of the lichen. WHC and specific thallus mass (STM) (mg DM/cm2) of the lichens were calculated. Bryoria spp. had a significantly lower STM compared to U. dasypoga and A. sarmentosa, due to its thinner branches and higher branch density. Bryoria also had a lower WHC compared to A. sarmentosa, promoting a rapid uptake and loss of water. All species had a significant relationship between STM and WHC, above a 1:1 line for all species except U. dasypoga. The lower relationship in U. dasypoga is explained by its less developed branching in combination with its thick branches