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| Titel |
Evidence for substantial forestry canopy processing of nitrogen deposition using isotopic tracer experiments in low deposition conditions |
| VerfasserIn |
Daniele Ferraretto, Kate Heal |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140293
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| Publikation (Nr.) |
 EGU/EGU2017-3660.pdf |
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| Zusammenfassung |
| Temperate forest ecosystems are significant sinks for nitrogen deposition (Ndep) yielding
benefits such as protection of waterbodies from eutrophication and enhanced sequestration of
atmospheric CO2. Previous studies have shown evidence of biological nitrification and Ndep
processing and retention in forest canopies. However, this was reported only at sites with
high environmental or experimentally enhanced rates of Ndep (∼18 kg N ha−1
y−1) and has not yet been demonstrated in low Ndep environments. We have used
bulk field hydrochemical measurements and labelled isotopic experiments to assess
canopy processing in a lower Ndep environment (∼7 kg N ha−1 year−1) at a Sitka
spruce plantation in Perthshire, Scotland, representing the dominant tree species
(24%) in woodlands in Great Britain. Analysis of 4.5 years of measured N fluxes in
rainfall (RF) and fogwater onto the canopy and throughfall (TF) and stemflow (SF)
below the canopy suggests strong transformation and uptake of Ndep in the forest
canopy. Annual canopy Ndep uptake was ∼4.7 kg N ha−1 year−1, representing
60-76% of annual Ndep. To validate these plot-scale results and track N uptake
within the forest canopy in different seasons, double 15N-labelled NH4NO3 (98%)
solution was sprayed in summer and winter onto the canopy of three trees at the
measurement site. RF, TF and SF samples have been collected and analysed for 15NH4 and
15NO3. Comparing the amount of labelled N recovered under the sample trees
with the measured δ15N signal is expected to provide further evidence of the role
of forest canopies in actively processing and retaining atmospheric N deposition. |
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