One year of transplant: Is it enough for lichens to reflect the new atmospheric conditions?

How long does it take a lichen to respond to changes (worsening or improvement) of atmospheric conditions is still discussed. We selected and removed lichen thalli (Flavoparmelia caperata) from sites subject to different intensities of pollution around a landfill in Central Italy and exposed them in a remote unpolluted area for 12 months. The content of elements of toxicological concern (As, Cd, Cr, Cu, Pb, Zn) and several physiological parameters in lichen thalli (chlorophyll a fluorescence emission, chlorophyll content and integrity, membrane lipid peroxidation, content of secondary metabolites and ergosterol content) were investigated before and after the recovery and hence compared with those of native (and clean) samples of the remote area. In an opposite trial, heavy metals content was investigated in samples taken from the remote area and exposed around the landfill. Values of the transplants were then compared with those of native samples at the landfill. From chemical point of view, the content of heavy metals decreased (by ca. 25%) in lichen thalli taken from the landfill and exposed in the remote area, however background values were never reached. On the other hand, lichen thalli taken from the remote area and exposed around the landfill accumulated up to ca. 80% of the content of in situ samples. The rate of accumulation was higher than the rate of element loss referred to the same temporal interval. The recovery of physiological parameters, especially those typical of the mycobiont or of the whole lichen symbiosis, was much faster than heavy metal detoxification, and after 12 months transplanted lichens already reflected the new environmental conditions at the remote site.