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| Titel |
Critical loads of nitrogen deposition and critical levels of atmospheric ammonia for semi-natural Mediterranean evergreen woodlands |
| VerfasserIn |
P. Pinho, M. R. Theobald, T. Dias, Y. S. Tang, C. Cruz, M. A. Martins-Loução, C. Máguas, M. Sutton, C. Branquinho |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 3 ; Nr. 9, no. 3 (2012-03-28), S.1205-1215 |
| Datensatznummer |
250006855
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| Publikation (Nr.) |
 copernicus.org/bg-9-1205-2012.pdf |
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| Zusammenfassung |
| Nitrogen (N) has emerged in recent years as a key factor associated with
global changes, with impacts on biodiversity, ecosystems functioning and
human health. In order to ameliorate the effects of excessive N, safety
thresholds such as critical loads (deposition fluxes) and levels
(concentrations) can be established. Few studies have assessed these
thresholds for semi-natural Mediterranean ecosystems. Our objective was
therefore to determine the critical loads of N deposition and long-term
critical levels of atmospheric ammonia for semi-natural Mediterranean
evergreen woodlands. We have considered changes in epiphytic lichen
communities, one of the most sensitive comunity indicators of excessive N in
the atmosphere. Based on a classification of lichen species according to
their tolerance to N we grouped species into response functional groups,
which we used as a tool to determine the critical loads and levels. This was
done for a Mediterranean climate in evergreen cork-oak woodlands, based on
the relation between lichen functional diversity and modelled N deposition
for critical loads and measured annual atmospheric ammonia concentrations
for critical levels, evaluated downwind from a reduced N source (a cattle
barn). Modelling the highly significant relationship between lichen
functional groups and annual atmospheric ammonia concentration showed the
critical level to be below 1.9 μg m−3, in agreement with recent
studies for other ecosystems. Modelling the highly significant relationship
between lichen functional groups and N deposition showed that the critical
load was lower than 26 kg (N) ha−1 yr−1, which is within the
upper range established for other semi-natural ecosystems. Taking into
account the high sensitivity of lichen communities to excessive N, these
values should aid development of policies to protect Mediterranean woodlands
from the initial effects of excessive N. |
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