Effects of nitrogen deposition and soil fertility on cover and physiology of Cladonia foliacea (Huds.) Willd., a lichen of biological soil crusts from Mediterranean Spain

We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha⁻¹ yr⁻¹ in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. β-carotene/chlorophylls increased with 20-50 kg N ha⁻¹ yr⁻¹ (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha⁻¹ yr⁻¹. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes.