Nitrogen and carbon contents and δ15N and δ13C signatures in six bryophyte species: assessment of long-term deposition changes (1980-2010) in Spanish beech forests

In this study we used recent (2010) and herbarium material (1980) of six bryophyte species to assess long-term atmospheric deposition in natural forested areas in northern Spain. For this purpose, tissue nitrogen and carbon content, as well as 13C and 15N signatures of samples of Hypnum cupressiforme, Polytrichastrum formosum, Leucobryum juniperoideum, Rhytidiadelphus loreus, Homalothecium lutescens and Diplophyllum albicans were analysed and comparisons made between years and species. In addition, the usefulness of each of the six species was evaluated. The range of values observed was similar to that in other studies carried out in rural areas. Significantly lower values were found in 2010 for N (H. cupressiforme), 15N (R. loreus and D. albicans), C (R. loreus) and 13C (all except L. juniperoideum). Our natural areas are thus now less influenced by atmospheric pollutants than they were, most probably due to changes in some traditional local activities. Differences were observed between species for all the four parameters studied, so different species must not be analysed together. Finally, R. loreus and H. lutescens seem to be good bioindicators, sensitive even with a few samples, although further studies are needed to corroborate their usefulness.