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| Titel |
Significant impacts of nutrient enrichment on High Arctic vegetation and soils despite two decades of recovery |
| VerfasserIn |
L. E. Street, N. R. Burns, S. J. Woodin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059078
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| Zusammenfassung |
| We re-visit a unique field manipulation study in Svalbard to assess the long-term recovery of
plant species composition, leaf tissue chemistry and total ecosystem carbon storage from
nutrient enrichment.
The experiment was established in 1991. The original aim was to quantify the ‘critical
load’ of nitrogen (N) for tundra; that is, the minimum rate of N deposition affecting
ecosystem structure and function. Dissolved N was applied to heath vegetation, both alone
and in combination with phosphorous (P), during the growing season over three years. The
rates of N addition were lower than in most other nutrient manipulation studies, and were
designed to represent typical rates of deposition in the Scottish highlands (50 kg N ha-1
yr-1) and maximum deposition rates experienced in the Arctic (10 kg N ha-1 yr-1).
Significant changes in shrub cover, the greenness and N content of the moss layer,
and the extent of ecosystem N saturation had occurred by the end of the treatment
period.
After 18 years of recovery without further treatment, we assessed primary productivity
using CO2 flux measurements, and the ‘greenness’ of vegetation using the Normalised
Difference Vegetation Index. We made destructive measurements of above- and
below-ground carbon and nutrient stocks, quantified species composition and sampled leaf
tissue for chemical analysis.
Total carbon storage in organic soils and vegetation was c. 40 % lower in the plots treated
with 50 kg N ha-1 yr-1 compared to controls. Species composition in N treated plots also
differed significantly, but there was no clear treatment effect on primary productivity.
Where 50 kg N ha-1 yr-1 was applied in combination with P (at 5 kg P ha-1 yr-1
), organic carbon storage was c. 70 % greater than controls, the vegetation was
greener, and primary productivity higher. Effects of the treatments were also still
clearly apparent in moss tissue nutrient status, even at the lower nitrogen application
rate.
Our results imply that the effects of nutrient enrichment on High Arctic ecosystems are
not readily reversible, and that short-term addition of N can result in long-term carbon losses.
We show that mosses perform an important role in retaining deposited N aboveground. Our
results also highlight the importance of P in mediating carbon cycle responses to increased N
availability. |
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