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| Titel |
Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone |
| VerfasserIn |
J. D. M. Speed, V. Martinsen, A. J. Hester, Ø. Holand, J. Mulder, A. Mysterud, G. Austrheim |
| 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 ; 12, no. 5 ; Nr. 12, no. 5 (2015-03-12), S.1615-1627 |
| Datensatznummer |
250117856
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| Publikation (Nr.) |
 copernicus.org/bg-12-1615-2015.pdf |
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| Zusammenfassung |
| Treelines differentiate vastly contrasting ecosystems: open tundra from
closed forest. Treeline advance has implications for the climate system due
to the impact of the transition from tundra to forest ecosystem on carbon
(C) storage and albedo. Treeline advance has been seen to increase
above-ground C stocks as low vegetation is replaced with trees but decrease
organic soil C stocks as old carbon is decomposed. However, studies
comparing across the treeline typically do not account for elevational
variation within the ecotone. Here we sample ecosystem C stocks along an
elevational gradient (970 to 1300 m), incorporating a large-scale and
long-term livestock grazing experiment, in the southern Norwegian mountains.
We investigate whether there are continuous or discontinuous changes in C
storage across the treeline ecotone, and whether these are modulated by
grazing. We find that vegetation C stock decreases with elevation, with a
clear breakpoint between the forest line and treeline above which the
vegetation C stock is constant. C stocks in organic surface horizons of the
soil were higher above the treeline than in the forest, whereas C stocks in
mineral soil horizons are unrelated to elevation. Total ecosystem C stocks
also showed a discontinuous elevational pattern, increasing with elevation
above the treeline (8 g m−2 per metre increase in elevation), but
decreasing with elevation below the forest line (−15 g m−2 per metre
increase in elevation), such that ecosystem C storage reaches a minimum
between the forest line and treeline. We did not find any effect of
short-term (12 years) grazing on the elevational patterns. Our findings
demonstrate that patterns of C storage across the treeline are complex, and
should be taken account of when estimating ecosystem C storage with shifting
treelines. |
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