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| Titel |
Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies |
| VerfasserIn |
L. Wang, A. Ibrom, J. F. J. Korhonen, K. F. Arnoud Frumau, J. Wu, M. Pihlatie, J. K. Schjoerring |
| 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. 2 ; Nr. 10, no. 2 (2013-02-13), S.999-1011 |
| Datensatznummer |
250017515
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| Publikation (Nr.) |
 copernicus.org/bg-10-999-2013.pdf |
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| Zusammenfassung |
| Seasonal and spatial variations in foliar nitrogen (N) parameters were
investigated in three European forests with different tree species, viz.
beech (Fagus sylvatica L.), Douglas fir (Pseudotsuga menziesii
(Mirb.) Franco) and Scots pine (Pinus sylvestris L.) growing in
Denmark, the Netherlands and Finland, respectively. The objectives were to
investigate the distribution of N pools within the canopies of the different
forests and to relate this distribution to factors and plant strategies
controlling leaf development throughout the seasonal course of a vegetation
period. Leaf N pools generally showed much higher seasonal and vertical
variability in beech than in the coniferous canopies. However, also the two
coniferous tree species behaved very differently with respect to peak summer
canopy N content and N re-translocation efficiency, showing that
generalisations on tree internal vs. ecosystem internal N cycling cannot be
made on the basis of the leaf duration alone. During phases of intensive N
turnover in spring and autumn, the NH4+ concentration in beech
leaves rose considerably, while fully developed green beech leaves had
relatively low tissue NH4+, similar to the steadily low levels in
Douglas fir and, particularly, in Scots pine. The ratio between bulk foliar
concentrations of NH4+ and H+, which is an indicator of the
NH3 emission potential, reflected differences in foliage N
concentration, with beech having the highest values followed by Douglas fir
and Scots pine. Irrespectively of the leaf habit, i.e. deciduous versus
evergreen, the majority of the canopy foliage N was retained within the
trees. This was accomplished through an effective N re-translocation
(beech), higher foliage longevity (fir) or both (boreal pine forest). In
combination with data from a literature review, a general relationship of
decreasing N re-translocation efficiency with the time needed for canopy
renewal was deduced, showing that leaves which live longer re-translocate
relatively less N during senescence. The Douglas fir stand, exposed to
relatively high atmospheric N deposition, had by far the largest peak summer
canopy N content and also returned the largest amount of N in foliage
litter, suggesting that higher N fertility leads to increased turnover in
the ecosystem N cycle with higher risks of losses such as leaching and gas
emissions. |
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