BIO-MONITORING FOR ATMOSPHERIC NITROGEN POLLUTION USING EPIPHYTIC LICHENS AND BRYOPHYTES JASON EDWARD JAMES LEWIS, BSc (Hons), MSc Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy APRIL 2012 Abstract Nitrogen enrichment in sensitive habitats has become a matter of concern in recent years, and has led to the need to develop a bio-monitoring scheme that could be used by non-specialists to undertake site evaluation across the UK. Epiphytes are ideal candidates for such a project due to their high sensitivity to atmospheric pollutants. Indicator species analysis identified a comprehensive UK-specific list of epiphytic indicators for NH3 pollution in the UK that for the first time also included microlichens. A shortlist of easily identifiable, widely distributed indicator species was produced from these and used to trial the effectiveness of a frequency based scoring system. A simple, un-weighted frequency based scoring system founded on the Lichen Acidophyte Nitrophyte index was found to correlate strongly with NH3 concentrations in air. Assessment of other atmospheric chemistry and climate variables with the scoring system showed that NO2 concentrations in air and bark pH were confounding factors. The influence of pH was further validated by observations in a field experimentation plot where different N forms were applied. In order to address this, a regression equation was formulated that incorporated NH3, NO2 and bark pH to produce a predictive model that could potentially be used to evaluate site condition with respect to atmospheric N pollution, as defined by the combined effect of NH3 and NO2. Investigations into the biochemistry of an indicator species identified that rates of phosphomonoesterase (PME) activity were higher in N-sensitive species than N-tolerant ones. N-sensitive lichen thallus pH measurements for were also consistently more acidic than those of N-tolerant species, and closer to the observed pH optima of PME activity. i Acknowledgements My sincerest gratitude goes to Prof. P.D. Crittenden for his invaluable supervision, guidance, advice and patience, without which the production of this PhD thesis would not have been possible. Thanks also the other four project supervisors/advisors: I.D. Leith, Dr. L.J. Shepherd and Prof. M.A. Sutton (CEH Edinburgh) and P.A. Wolseley (NHM) for their assistance in a wide variety of matters ranging from technical support to fieldwork assistance and collection of material during the course of this research project. I would also like to thank my mother and sister for their support during the last four years; and a special thank you to C. Puglisi for her time, patience, support and field assistance at Dunalastair Estate, Grizedale Forest, Mere Sands Wood and Rannoch. A big note of thanks is also extended to N. Van Dijk (CEH Edinburgh) and M. McMullen (NIEA). Netty provided critical advice and guidance on the analysis of ALPHA samplers, and field assistance at Banchory, Glenmore Wood, Strath Vaich and Wood of Cree. Melina was instrumental in the identification and acquisition of N. Ireland survey sites, assisting in the surveying of Lough Navar, and arranging the collection of ALPHA sampler badges across the N. Ireland sites. Many thanks also to A. Chadwick (FC), M. Chesman, J. Fairburn (SEPA), M. Senkans, L. Turner, R. Langston and P. Wilson (SEPA) who also helped in the collection of ALPHA samplers from survey sites. ii I would also like to thank Dr. D Chapman and Dr. T. Dore (CEH Edinburgh) for providing the modelled climate and FRAME concentration data respectively; and Maggie Hatton-Ellis and Dylan Lloyd (CCW) for permitting access to the ECBN [NH3] data for Tycanol Wood. CEH Lancaster for providing the results of the chemical analysis of lichen thallus material. Dr. B. J. Coppins and J. Abbott-Wells for helping with the identification and recording of lichen species. P. Lambley for collecting lichen material used in the thallus pH analysis, and Dr. C.J. Ellis for his statistical advice, particularly in relation to the ordination analyses. A final note of gratitude needs to be expressed to SNIFFER, SEPA, NIEA and SNH for funding this research project; and the University of Nottingham for its financial assistance during the write up of this thesis. iii Table of Contents Chapter 1. Introduction ............................................................................. 1 1.1 Background ............................................................................................. 1 1.2 Nitrogen .................................................................................................. 5 1.2.1 The Various Forms and Effects of Atmospheric N .................... 5 1.2.2 N and Epiphytic Communities ................................................... 8 1.2.3 N and Bark pH .......................................................................... 10 1.3 Epiphytes as Bio-monitors .................................................................... 12 1.3.1 Ellenberg Index ......................................................................... 13 1.3.2 Acidofiele Indicatie Waarde and Nitrofiele Indicatie Waarde Indices ....................................................................................... 15 1.3.3 LA/LN and LAN Indices ............................................................. 16 1.4 Potentially Confounding Variables....................................................... 17 1.4.1 Abiotic Factors.......................................................................... 18 1.4.1.1 Precipitation and Occult Precipitation .......................... 18 1.4.1.2 Altitude and Temperature ............................................. 20 1.4.1.3 Exposure to Sunlight (Irradiance and Aridity) ............. 21 1.4.1.4 Sulphur Dioxide ............................................................ 21 1.4.1.5 Geology, Pedology and Dust ........................................ 23 1.4.1.6 Site History ................................................................... 25 1.4.1.7 Aspect and Inclination .................................................. 25 1.4.1.8 Bark Topography .......................................................... 26 1.4.1.9 Bark Sloughing ............................................................. 27 1.4.2 Biotic Factors ............................................................................ 28 1.4.2.1 Bark Age ....................................................................... 28 1.4.2.2 Bark pH ......................................................................... 28 1.4.2.3 Grazing ......................................................................... 30 1.4.2.4 Competition .................................................................. 32 1.4.2.5 Succession..................................................................... 34 1.5 Aims and Objectives of the Present Work ............................................ 35 Chapter 2. Regional-Scale Survey Methods ............................................ 37 2.1 Introduction........................................................................................... 37 2.2 Criteria for Site Selection ..................................................................... 38 2.2.1 Climatic and Air Chemistry Variables ..................................... 38 2.2.2 Landscape Factors .................................................................... 39 2.2.3 Tree Availability ....................................................................... 40 iv 2.3 Climate Data ......................................................................................... 40 2.3.1 Oceanicity ................................................................................. 41 2.3.2 Preliminary Analysis of Climatic Variables ............................. 41 2.4 Measured Environmental Variables ..................................................... 42 2.5 NH3 Monitoring .................................................................................... 43 2.5.1 ALPHA Sampler Preparation ................................................... 45 2.5.2 ALPHA Sampler Installation .................................................... 47 2.5.3 ALPHA Sampler Analysis ........................................................ 48 2.5.4 Calculating Atmospheric NH3 Concentrations ......................... 48 2.6 Modelled Environmental Variables ...................................................... 50 2.7 Preliminary Analysis of Environmental Variables ............................... 51 2.7.1 Correlation Analysis of Modelled and Measured Concentration Data for Regional-Scale Survey Sites ....................................... 51 2.7.2 Assessment of Measured Data .................................................. 52 2.7.3 Assessment of Correlations between Variables ........................ 52 2.8 Biological Survey ................................................................................. 53 2.8.1 Tree Distance from Monitoring Station .................................... 56 2.8.2 Tree Age and Bark Topography ............................................... 57 2.9 Trunk Epiphyte Survey ......................................................................... 58 2.10 Branch Epiphyte Survey ....................................................................... 60 2.11 Species Identification............................................................................ 60 2.12 Bark pH Measurements ........................................................................ 62 2.12.1