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| Titel |
New foliage growth is a significant, unaccounted source for volatiles in boreal evergreen forests |
| VerfasserIn |
J. Aalto, P. Kolari, P. Hari, V.-M. Kerminen, P. Schiestl-Aalto, H. Aaltonen, J. Levula, E. Siivola, M. Kulmala  , J. Bäck |
| 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 ; 11, no. 5 ; Nr. 11, no. 5 (2014-03-06), S.1331-1344 |
| Datensatznummer |
250117273
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| Publikation (Nr.) |
 copernicus.org/bg-11-1331-2014.pdf |
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| Zusammenfassung |
| Estimates of volatile organic compound (VOC) emissions from forests are based
on the assumption that foliage has a steady emission potential over its
lifetime, and that emissions are mainly modified by short-term variations in
light and temperature. However, in many field studies this has been
challenged, and high emissions and atmospheric concentrations have been
measured during periods of low biological activity, such as in springtime. We
conducted measurements during three years, using an online gas-exchange
monitoring system to observe volatile organic emissions from a mature
(1 year-old) and a growing Scots pine shoot. The emission rates of organic
vapors from vegetative buds of Scots pine during the dehardening and rapid
shoot growth stages were one to two orders of magnitude higher than those
from mature foliage; this difference decreased and finally disappeared when
the new shoot was maturing in late summer. On average, the springtime
monoterpene emission rate of the bud was about 500 times higher than that of
the mature needles; during the most intensive needle elongation period, the
monoterpene emission rate of the growing needles was 3.5 higher than that of
the mature needles, and in September the monoterpene emission rate of the
same years' needles was even lower (50%) than that of the previous
years' needles. For other measured compounds (methanol, acetone and
methylbutenol) the values were of the same order of magnitude, except before
bud break in spring, when the emission rates of buds for those compounds were
on average about 20–30 times higher than that of mature needles. During
spring and early summer the buds and growing shoots are a strong source of
several VOCs, and if they are not accounted for in emission modeling a
significant proportion of the emissions – from a few percent to even half of
the annual cumulative emissions – will remain concealed. The diurnal
emission pattern of growing shoots differed from the diurnal cycle in
temperature as well as from the diurnal emission pattern of mature shoots,
which may be related to processes involved in shoot or needle elongation. Our
findings imply that global estimations of monoterpene emission rates from
forests are in need of revision, and that the physiological state of the
plants should be taken into account when emissions of the reactive gases such
as monoterpenes are estimated. |
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