Collation of evidence of nitrogen impacts on vegetation in relation to UK biodiversity objectives
The analysis presented in Report 447 represents the first part of a large study of nitrogen impacts on vegetation.
This report presents the largest analysis of national vegetation
data sets in relation to nitrogen (N) deposition carried out to
date. The study statistically analysed eight independent
national vegetation surveillance datasets using a consistent
approach, to identify evidence of N deposition impacts in four
habitat types; acidic and calcareous grassland, heathland and
This new analysis was the largest of its kind, using data from
the Vascular Plant Database (1930-1969 and 1987-1999), BSBI Local
Change Survey (1987-1988 and 2003-2004), British Bryological
Society, British Lichen Society, Plantlife Common Plant Survey, and
three country grassland datasets. The project took four widespread
habitats, calcareous and acid grasslands, heathlands, and bogs, and
for each, looked for evidence of vegetation change caused by
nitrogen deposition, after accounting for other factors that could
have an impact. Spatial analysis, and where possible temporal
analysis, was conducted to analyse the relationship between N
deposition and summary variables (Ellenberg scores, canopy height,
specific leaf area), species diversity (species richness,
Shannon-Wiener diversity index) and individual species
The study clearly demonstrated significant changes in the
abundance of individual species and variables describing habitat
structure and function as a result of N deposition. This,
together with previous evidence from surveys and experiments,
provides clear evidence of species-level impacts of N deposition in
all four of the habitats investigated.
Results are presented individually for each of the datasets
examined. The discussion section draws the results together
examining them for each habitat. Key results are provided in
the results section of the report. A complete set of all
significant results are presented in the Electronic Appendix.
The analysis presented in Report 447 represents the first part
of a large study of nitrogen impacts on vegetation. In a
second part of the project, reported in JNCC Report 449, the
results of this new analysis, together with other sources of
independent evidence, are interpreted in respect of implications
for “conservation commitments”.
A project summary, presenting the key messages and summarising
the impacts, is also provided.
Please cite as: Stevens, C.J., Smart, S.M., Henrys, P., Maskell, L.C., Walker, K.J., Preston, C.D., Crowe, A., Rowe, E., Gowing, D.J. & Emmett, B.A., (2011), Collation of evidence of nitrogen impacts on vegetation in relation to UK biodiversity objectives, JNCC Report 447, ISSN 0963–8091