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| Titel |
Implications of albedo changes following afforestation on the benefits of forests as carbon sinks |
| VerfasserIn |
M. U. F. Kirschbaum, D. Whitehead, S. M. Dean, P. N. Beets, J. D. Shepherd, A.-G. E. Ausseil |
| 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 ; 8, no. 12 ; Nr. 8, no. 12 (2011-12-15), S.3687-3696 |
| Datensatznummer |
250006249
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| Publikation (Nr.) |
 copernicus.org/bg-8-3687-2011.pdf |
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| Zusammenfassung |
Increased carbon storage with afforestation leads to a
decrease in atmospheric carbon dioxide concentration and thus decreases
radiative forcing and cools the Earth. However, afforestation also changes
the reflective properties of the surface vegetation from more reflective
pasture to relatively less reflective forest cover. This increase in
radiation absorption by the forest constitutes an increase in radiative
forcing, with a warming effect. The net effect of decreased albedo and
carbon storage on radiative forcing depends on the relative magnitude of
these two opposing processes.
We used data from an intensively studied site in New Zealand's Central North
Island that has long-term, ground-based measurements of albedo over the full
short-wave spectrum from a developing Pinus radiata forest. Data from this site were
supplemented with satellite-derived albedo estimates from New Zealand
pastures. The albedo of a well-established forest was measured as 13 % and
pasture albedo as 20 %. We used these data to calculate the direct
radiative forcing effect of changing albedo as the forest grew.
We calculated the radiative forcing resulting from the removal of carbon
from the atmosphere as a decrease in radiative forcing of
−104 GJ tC−1 yr−1. We also showed that the observed change in
albedo constituted a direct radiative forcing of
2759 GJ ha−1 yr−1. Thus, following afforestation,
26.5 tC ha−1 needs to be stored in a growing forest to balance the
increase in radiative forcing resulting from the observed albedo change.
Measurements of tree biomass and albedo were used to estimate the net change
in radiative forcing as the newly planted forest grew. Albedo and
carbon-storage effects were of similar magnitude for the first four to five
years after tree planting, but as the stand grew older, the carbon storage
effect increasingly dominated. Averaged over the whole length of the
rotation, the changes in albedo negated the benefits from increased carbon
storage by 17–24 %. |
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