Predicting lichen hydration using biophysical models |
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Authors: | Anna V Jonsson Jon Moen Kristin Palmqvist |
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Institution: | 1.Department of Ecology and Environmental Science,Ume? University,Ume?,Sweden |
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Abstract: | Two models for predicting the hydration status of lichens were developed as a first step towards a mechanistic lichen productivity
model. A biophysical model included the water potential of the air, derived from measurements of air temperature, relative
humidity and species-specific rate constants for desiccation and rehydration. A reduced physical model, included only environmental
parameters, assuming instantaneous equilibration between the lichen and the air. These models were developed using field and
laboratory data for three green algal lichens: the foliose epiphytic Platismatia glauca (L.) W. Culb., the fruticose epiphytic Alectoria sarmentosa (Ach.) Ach. and the fruticose, terricolous and mat-forming Cladina rangiferina (L.) Weber ex Wigg. The models were compared and validated for the same three species using data from a habitat with a different
microclimate. Both models predicted the length and timing of lichen hydration periods, with those for A. sarmentosa and P. glauca being highly accurate—nearly 100% of the total wet time was predicted by both the biophysical and physical models. These
models also predicted an accurate timing of the total realized wet time for A. sarmentosa and P. glauca when the lichens were wet. The model accuracy was lower for C. rangiferina compared to the epiphytes, both for the total realized wet time and for the accuracy of the timing for the hydration period.
These results demonstrate that the stochastic and continually varying hydration status of lichens can be simulated from biophysical
data. Further development of these models to also include water-related activity, light and temperature conditions during
the hydration events will then be a potent tool to assess potential lichen productivity in landscapes and habitats of various
microclimatic conditions. |
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Keywords: | Air humidity Elasticity analysis Microclimate Water content Water potential |
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