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P. Matos et al. 2010. Can lichen functional diversity be a good indicator of macroclimatic conditions
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By using three different functional groups we were able to observe shifts in the communities
along the climatic gradient. Precipitation, evapotranspiration and relative air humidity were the
variables that explained better the shifts from hygrophytic to xerophytic lichen communities. In
a Liguria case study, Girodani and Incerti (2008) found that 30% of its observed lichen flora
was significantly correlated with yearly average temperature and rainfall patterns. This
correlation allowed them to identify 3 guilds of species significantly sensitive to these climatic
variables: species mainly related to cold-humid climate, species related to humid conditions but
occurring in a wider range of temperatures and species occurring in meso to warm areas with
humid to dry climate. Although not using the same functional groups, our results show a similar
tendency, not evidenced by a group of individual species as in the former study, but with an a
priori selected functional-group related to humidity requirements. Above 1400 mm in average
of precipitation the hygrophytic community clearly dominated (>50%) over the mesophytic or
the xerophytic ones, whereas below 600 mm it corresponded to only one third of the community.
The xerophytic community increased clearly and consistently only when the precipitation was
below approximately 600 mm. The mesophytic group showed an intermediate behavior. With
increasing evapotranspiration the hygrophytic lichens showed a constant increase in relative
average and also in variance. Again the xerophytic community responded more clearly only
below 450 mm of evapotranspiration.
The hygrophytic lichens responded negatively to increasing insolation, solar radiation and
temperature, although that was not as clear as observed for precipitation and evapotranspiration.
This decrease in LDV of hygrophytic lichens was associated with an increase in xerophytic ones.
These sets of variables (insolation, solar radiation and temperature) induce small changes in the
median, and seem to change the variance of the response of the lichen communities.
The group of functional indicators used/applied in this work can be very important in the current
context of climate change. It was predicted for the Mediterranean region an increase in drought
conditions, due to higher temperature and reduced precipitation (IPCC 2007). This work
confirms that changes in macroclimatic conditions leads to changes in the functional structure of
the lichen communities. Further studies are needed to evaluate the use of these indicators along
time. Moreover, changes along smaller spatial scales should also be tested. The results of this
work suggested that changes in sensitive lichen communities could be used as an indicator of
macroclimatic changes in space.
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