The concentration of nitrogen in nitrophilous and non-nitrophilous lichen species

The purpose of this work was to compare nitrogen concentrations in Xanthori a parietina, a nitrophilous lichen species, with non-nitrophilous species ( Ramalina fastigiata, Parmelia caperata and Evernia prunastri). In order to understand the differences between nitrophilous and non-nitrophilous lichen species, total nitrogen concentrations, the organic and inorganic nitrogen fractions, the deposited nitrogen on thallus surface and the cation exchan ge capacity were determined. The nitrophilous species X. parietina presente d always higher nitrogen concentrations than the other studied species, whe n collected at the same sites. The spatial variation in nitrogen concentrat ion in this lichen species reflects the amount of deposited nitrogen, parti cularly ammonium. No deposited nitrogen was detected on the thallus surface of both X. parietina and X. fastigiata. The scarce amount of nitrogen on t he thallus surface was probably hampered by the level of organic nitrogen f rom the whole thallus. The proportion of inorganic nitrogen in relation to the total concentration seems to reflect nitrogen sources. The lowest catio n exchange capacity found for X. parietina can be a contribution to the und erstanding of the tolerance mechanisms of this nitrophilous species. Moreov er, E. prunastri, an acidophilous lichen species, presented the highest cat ion exchange capacity of all the studied species.