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| Titel |
Does N deposition affect canopy N status and global albedo? |
| VerfasserIn |
M. Borghetti, A. Nolè, S. Raddi, F. Magnani |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029730
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| Zusammenfassung |
| Atmospheric nitrogen deposition over the last century has resulted in substantial changes in soil C:N ratios in many regions, with potentially important effects on site fertility and plant nutritional status. This is expected to reflect in forest leaf N concentration and forest productivity, and eventually in an increase in forest C sequestration.
In a recent study (Ollinger et al. 2008. PNAS 105, 19335-19340) canopy N concentration and forest gross primary production have been found to be significantly correlated with canopy VIS-NIR albedo, as derived from MODIS imagery, paving the way for a global asessment of forest N status and its possible relationship with atmospheric N deposition.
Here we show that, on a global scale, forest albedo is indeed correlated with N deposition, as estimated by the TM3 atmospheric transport model. Although partly the result of inter-specific differences in leaf and canopy reflectance and of the chance correlation between N deposition and biome distribution, the relationship appears to hold true also for individual plant functional types. Canopy albedo is found to increase significantly with N deposition up to a threshold of about 10-15 kg N ha-1 yr-1, and to remain constant or slightly decline above this level. This would suggest a saturation of canopy N concentration (and potentially forest productivity and C sequestration) above this level. A shallower relationship is observed in tropical than in temperate and boreal forests, in good agreement with our current understanding of N saturation. Apart from the implications for the assessment of forest productivity and C sequestration, the new findings suggest a novel and potentially relevant effect of atmospheric N deposition on Climate Change, though its impact of canopy albedo itself. |
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