Citizen science identifies the effects of nitrogen deposition, climate and tree species on epiphytic lichens across the UK

Welden, N.A. , Wolseley, P.A. and Ashmore, M.R. (2018) Citizen science identifies the effects of nitrogen deposition, climate and tree species on epiphytic lichens across the UK. Environmental Pollution, 232, 80 - 89. (PMID:28967570)

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Abstract

A national citizen survey quantified the abundance of epiphytic lichens that are known to be either sensitive or tolerant to nitrogen (N) deposition. Records were collected across the UK from over 10,000 individual trees of 22 deciduous species. Mean abundance of tolerant and sensitive lichens was related to mean N deposition rates and climatic variables at a 5 km scale, and the response of lichens was compared on the three most common trees (Quercus, Fraxinus and Acer) and by assigning all 22 tree species to three bark pH groups. The abundance of N-sensitive lichens on trunks decreased with increasing total N deposition, while that of N-tolerant lichens increased. The abundance of N-sensitive lichens on trunks was reduced close to a busy road, while the abundance of N-tolerant lichens increased. The abundance of N-tolerant lichen species on trunks was lower on Quercus and other low bark pH species, but the abundance of N-sensitive lichens was similar on different tree species. Lichen abundance relationships with total N deposition did not differ between tree species or bark pH groups. The response of N-sensitive lichens to reduced nitrogen was greater than to oxidised N, and the response of N-tolerant lichens was greater to oxidised N than to reduced N. There were differences in the response of N-sensitive and N-tolerant lichens to rainfall, humidity and temperature. Relationships with N deposition and climatic variables were similar for lichen presence on twigs as for lichen abundance on trunks, but N-sensitive lichens increased, rather than decreased, on twigs of Quercus/low bark pH species. The results demonstrate the unique power of citizen science to detect and quantify the air pollution impacts over a wide geographical range, and specifically to contribute to understanding of lichen responses to different chemical forms of N deposition, local pollution sources and bark chemistry.

Item Type:Articles
Additional Information:We are grateful to the Big Lottery Fund for funding the OPAL project.
Keywords:Citizen science, nitrogen deposition, epiphytic lichens
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Welden, Dr Natalie
Authors: Welden, N.A., Wolseley, P.A., and Ashmore, M.R.
College/School:College of Social Sciences > School of Interdisciplinary Studies
Journal Name:Environmental Pollution
Publisher:Elsevier
ISSN:0269-7491
ISSN (Online):1873-6424
Published Online:28 September 2017

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