Nitrogen deposition enhances moss growth, but leads to an overall decline in habitat condition of mountain moss-sedge heath

Heather F. Armitage, Andrea J. Britton, Rene van der Wal, Imogen S. K. Pearce, Des B. A. Thompson, Sarah J. Woodin

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Ecosystems are subject to multiple, natural and anthropogenic environmental influences, including nitrogen (N) deposition, land use and climate. Assessment of the relative importance of these influences on biodiversity and ecosystem functioning is crucial for guiding policy and management decisions to mitigate global change; yet, few studies consider multiple drivers. In the UK, ongoing loss of the internationally important arctic/alpine moss-sedge community, Racomitrium heath, has been linked to elevated N deposition, high grazing pressures and their combination; however, the relative importance of these drivers remains unclear. We used environmental gradients across the habitat's European distribution (UK, Faroes, Norway and Iceland) to investigate the relative impact of N deposition and grazing pressure, as well as climate, on the condition of the dominant moss species, Racomitrium lanuginosum. Key variables including tissue chemistry, growth and cover were measured at 36 sites, and multiple linear regressions were used to examine the relative importance of the drivers across sites. Our results clearly show that regional variation in the condition of R. lanuginosum across Europe is primarily associated with the impacts of N deposition, with climate (air temperature) and grazing pressure playing secondary roles. In contrast to previous experimental studies, we found moss growth to be stimulated by elevated N deposition; this apparent discrepancy may result from the use of artificially high N concentrations in many experiments. Despite increased growth rates, we found that moss mat depth and cover declined in response to N deposition. Our results suggest that this is due to increased decomposition of material in the moss mat, which ultimately leads to loss of moss cover and habitat degradation. This study clearly demonstrates both the key role of N deposition in degradation of Racomitrium heath and the importance of observational studies along natural gradients for testing predictions from experimental studies in the real world.

Original languageEnglish
Pages (from-to)290-300
Number of pages11
JournalGlobal Change Biology
Volume18
Issue number1
Early online date31 Jul 2011
DOIs
Publication statusPublished - Jan 2012

Fingerprint

sedge
moss
Nitrogen
mountain
nitrogen
habitat
grazing pressure
Ecosystems
climate
experimental study
Degradation
degradation
ecosystem
Biodiversity
environmental gradient
Linear regression
Land use
global change
air temperature
biodiversity

Keywords

  • alpine
  • bryophytes
  • climate
  • grazing
  • growth
  • nitrogen deposition
  • Racomitrium heath
  • Racomitrium lanuginosum
  • tissue N

Cite this

Nitrogen deposition enhances moss growth, but leads to an overall decline in habitat condition of mountain moss-sedge heath. / Armitage, Heather F.; Britton, Andrea J.; van der Wal, Rene; Pearce, Imogen S. K.; Thompson, Des B. A.; Woodin, Sarah J.

In: Global Change Biology, Vol. 18, No. 1, 01.2012, p. 290-300.

Research output: Contribution to journalArticle

Armitage, Heather F. ; Britton, Andrea J. ; van der Wal, Rene ; Pearce, Imogen S. K. ; Thompson, Des B. A. ; Woodin, Sarah J. / Nitrogen deposition enhances moss growth, but leads to an overall decline in habitat condition of mountain moss-sedge heath. In: Global Change Biology. 2012 ; Vol. 18, No. 1. pp. 290-300.
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AB - Ecosystems are subject to multiple, natural and anthropogenic environmental influences, including nitrogen (N) deposition, land use and climate. Assessment of the relative importance of these influences on biodiversity and ecosystem functioning is crucial for guiding policy and management decisions to mitigate global change; yet, few studies consider multiple drivers. In the UK, ongoing loss of the internationally important arctic/alpine moss-sedge community, Racomitrium heath, has been linked to elevated N deposition, high grazing pressures and their combination; however, the relative importance of these drivers remains unclear. We used environmental gradients across the habitat's European distribution (UK, Faroes, Norway and Iceland) to investigate the relative impact of N deposition and grazing pressure, as well as climate, on the condition of the dominant moss species, Racomitrium lanuginosum. Key variables including tissue chemistry, growth and cover were measured at 36 sites, and multiple linear regressions were used to examine the relative importance of the drivers across sites. Our results clearly show that regional variation in the condition of R. lanuginosum across Europe is primarily associated with the impacts of N deposition, with climate (air temperature) and grazing pressure playing secondary roles. In contrast to previous experimental studies, we found moss growth to be stimulated by elevated N deposition; this apparent discrepancy may result from the use of artificially high N concentrations in many experiments. Despite increased growth rates, we found that moss mat depth and cover declined in response to N deposition. Our results suggest that this is due to increased decomposition of material in the moss mat, which ultimately leads to loss of moss cover and habitat degradation. This study clearly demonstrates both the key role of N deposition in degradation of Racomitrium heath and the importance of observational studies along natural gradients for testing predictions from experimental studies in the real world.

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