Lichens as biomarkers for dew amount and duration in the Negev Desert

We studied the lichen diversity on cobbles at 18 stations located within 4 aspects of a second order drainage basin near Sede Boqer at the Negev Highlands, Israel, where dew was found to be the main water source for lichens. At each station 10 cobbles were randomly chosen and the lichen community composition and structure were investigated and compared to the dew amount and duration that characterize each station. Excluding the wadi stations that showed a very heterogeneous population (probably originating from cobbles that rolled down from both adjacent slopes) and were therefore excluded from the analysis, all other stations were grouped into 5 clusters that showed a close link with the dew moisture regime. Lichen distribution pointed to species which can serve as biomarkers for dew amount and especially for dew duration. The data imply that at a meso-scale, lichens can provide information regarding the dew regime of habitats where no microclimatological data are available.