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| Titel |
Increased soil temperature and atmospheric N deposition have no effect on the N status and growth of a mature balsam fir forest |
| VerfasserIn |
L. D'Orangeville, D. Houle, B. Côté, L. Duchesne, H. Morin |
| 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 ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-11), S.4627-4639 |
| Datensatznummer |
250018334
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| Publikation (Nr.) |
 copernicus.org/bg-10-4627-2013.pdf |
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| Zusammenfassung |
Nitrogen (N) is a major growth-limiting factor in boreal forest ecosystems.
Increases of temperature and atmospheric N deposition are expected to affect
forest growth directly and indirectly by increasing N availability due to
higher rates of N mineralization. In order to understand the potential
impacts of these changes, a mature balsam fir stand in Québec, Canada,
was subjected during three consecutive growing seasons (2009–2011) to (i)
experimentally increased soil temperature (4 °C) and earlier
snowmelt (2–3 weeks) as well as (ii) increased inorganic N concentration in
artificial precipitation (3 × current N concentrations using
15NH4-15NO3). Soil inorganic N was measured using buried
ion-exchange membranes (PRS™ probes) and standard soil extractions.
Dendrometers were used to monitor the variations in diameter growth and
needles were analyzed annually for N to assess the nutritional response of
trees. Results from the second (2010) and third (2011) year of treatment are
reported.
After three years of treatment, there was no significant increase in soil
nitrate (NO3) or ammonium (NH4) availability either in the
organic or in the mineral soil as measured with standard soil extractions.
Similar results were obtained with ion-exchange membranes, except for
NH4 in the forest floor, which increased by an average of 54% over
the two years. No effect of treatments were observed on needle N or diameter
growth, but an 8-day earlier peak in diameter growth was measured in
heated plots in 2010.
We attributed the limited effects of our treatments to the acute soil
competition for available N at the site. As a result, the projected
modifications of the forest N cycle and concomitant increased forest growth
due to an earlier snowmelt, increased soil temperature and N deposition
should be considered with caution in similar cold N-poor ecosystems. |
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