A study of the epiphytic communities of Atlantic oak woods along an atmospheric nitrogen deposition gradient

1 Atlantic oak woods are of high conservation value and contain many rare lichens and bryophytes. The effects of nitrogen pollution on these epiphytic communities have not been previously studied. We investigated the composition of Atlantic oak wood epiphytic communities in relation to atmospheric N deposition in order to identify N indicator species and propose a critical load for such communities. 2 The epiphytic communities of seven Atlantic oak woods receiving estimated total nitrogen deposition in the range 10–53 kg N ha−1 year−1 were surveyed. Exposure of epiphytes to atmospheric N over 7 months was measured in terms of stemflow flux and concentration and airborne NH3. 3 Redundancy analysis (RDA) related the species to stemflow chemistry and bark pH. Different groups of species were found at (i) a coastal low N deposition site (Graphina ruiziana, Lecania cyrtella, Lobaria pulmonaria, Opegrapha atra, Orthotrichum affine, Melanelia fuliginosa ssp. glabratula and Pertusaria hymenea), (ii) inland low N deposition sites (I. myosuroides, F. tamarisci, Plagiochila atlantica, Cladonia chlorophaea, C. squamosa, Hypotrachyna laevigata and Thelotrema lepadinum) and (iii) high N deposition sites (Hypnun andoi, Hypnum cupressiforme, Calicium viride, Chrysothrix candelaris, C. coniocraea, Hypogymnia physodes, Parmelia saxatilis, Phyllospora rosei and Usnea subfloridana). 4 RDA analysis showed that bark pH and concentration in the stemflow explained the greatest amount of variation in the species composition among the sites. The sites separated into two groups (low and high concentration) leading to an estimate for the critical load for N deposition for epiphytes in Atlantic oak woods of 11–18 kg N ha−1 year−1. 5 Analysis of the occurrence of species against N levels suggested that I. myosuroides and F. tamarisci are indicators of small N inputs, whereas H. andoi, C. coniocraea, P. saxatilis and H. physodes are tolerant of increased N loads. 6 Different forms of N (, , NH3) were found to significantly affect the occurrence of different species. Some species were sensitive to total flux while others were sensitive to concentration.

[1]  J. Cape,et al.  Growth and tissue nitrogen of epiphytic Atlantic bryophytes: effects of increased and decreased atmospheric N deposition , 2004 .

[2]  J. W. Bates,et al.  Epiphyte differentiation between Quercus petraea and Fraxinus excelsior trees in a maritime area of South West England , 1981, Vegetatio.

[3]  K. Palmqvist,et al.  Carbon and nitrogen distribution in the green algal lichens Hypogymnia physodes and Platismatia glauca in relation to nutrient supply , 2003, Planta.

[4]  Ter Braak,et al.  Canoco reference manual and CanoDraw for Windows user''s guide: software for canonical community ord , 2002 .

[5]  J. Cape,et al.  Development and Types of Passive Samplers for Monitoring Atmospheric NO2 and NH3 Concentrations , 2001, TheScientificWorldJournal.

[6]  Mark A. Sutton,et al.  Regional estimation of pollutant gas dry deposition in the UK: model description, sensitivity analyses and outputs , 2000 .

[7]  C. M. V. Herk.  Mapping of Ammonia Pollution with Epiphytic Lichens in the Netherlands , 1999, The Lichenologist.

[8]  Markus Amann,et al.  Transboundary air pollution , 1999 .

[9]  P. Crittenden,et al.  Relationships between atmospheric nitrogen inputs and the vertical nitrogen and phosphorus concentration gradients in the lichen Cladonia portentosa. , 1998, The New phytologist.

[10]  L. Gustafsson,et al.  Factors of importance for the epiphytic vegetation of aspen Populus tremula with special emphasis on bark chemistry and soil chemistry , 1995 .

[11]  Y. Gauslaa.  The Lobarion, an Epiphytic Community of Ancient Forests Threatened by Acid Rain , 1995, The Lichenologist.

[12]  J. W. Bates.  Responses of the mosses Brachythecium rutabulum and Pseudoscleropodium purum to a mineral nutrient pulse , 1994 .

[13]  N. Hodgetts.  Atlas of the bryophytes of Britain and Ireland. Volume 3. Mosses (Diplolepideae): Edited by M. O. Hill, C. D. Preston & A. J. E. Smith. Harley Books, Colchester. 1994. 419 pp. ISBN 0 946589 31 3. Price: £30.00 , 1994 .

[14]  O. W. Purvis.  The Lichen Flora of Great Britain and Ireland , 1993 .

[15]  H. Siebel.  Indicatiegetallen van blad- en levermossen , 1993 .

[16]  J. W. Bates.  Influence of chemical and physical factors on Quercus and Fraxinus epiphytes at Loch Sunart, western Scotland : a multivariate analysis , 1992 .

[17]  John A. Lee,et al.  Effects of nitrogen oxides on nitrate assimilation in bryophytes , 1992 .

[18]  M. Hill,et al.  Atlas of the Bryophytes of Britain and Ireland - Volume 2: Mosses (Except Diplolepideae) , 1992 .

[19]  A. Farmer,et al.  Seasonal variations in acidic pollutant inputs and their effects on the chemistry of stemflow, bark and epiphyte tissues in three oak woodlands in N.W. Britain , 1991 .

[20]  A. Farmer,et al.  Comparisons of three woodland sites in NW Britain differing in richness of the epiphytic Lobarion pulmonariae community and levels of wet acidic deposition , 1991 .

[21]  M. Hill,et al.  Atlas of the Bryophytes of Britain and Ireland - Volume 1: Liverworts (Hepaticae and Anthocerotae) , 1991 .

[22]  A. Farmer,et al.  A Comparison of Methods for the Measurement of Bark PH , 1990, The Lichenologist.

[23]  A. Farmer,et al.  Epiphyte recolonization of oaks along a gradient of air pollution in South-East England, 1979-1990. , 1990, Environmental pollution.

[24]  A. Rowland.  An automated method for the determination of ammonium‐n in ecological materials , 1983 .

[25]  J. Hunt.  Dilute hydrochloric acid extraction of plant material for routine cation analysis , 1982 .

[26]  T. H. Nash.  Sensitivity of Lichens to Nitrogen Dioxide Fumigations , 1976 .

[27]  J. B. Kenworthy,et al.  Chemical Analysis of Ecological Materials. , 1976 .

[28]  D. Ratcliffe.  AN ECOLOGICAL ACCOUNT OF ATLANTIC BRYOPHYTES IN THE BRITISH ISLES , 1968 .