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| Titel |
Stable C and O isotope signals of drought in Mediterranean pines on inter- and intra-annual scales |
| VerfasserIn |
D. Sarris, R. Siegwolf, Ch. Körner |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068069
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| Zusammenfassung |
| In dry years radial growth for Pinus halepensis (a Mediterranean conifer) does not extend
into late spring/early summer, where drought impact should be the strongest. This lack of
assimilation and tissue formation should not allow the accurate recording of the stable
isotopic signal related to severe drought stress on tree-rings. However, on an inter-annual
scale of 30 years drought clearly reduced tree-ring width and 13C discrimination (Δ).
Inta-annually the highest δ13C signals were found in early to mid autumn (on the second
growth period after the growth cessation due to summer drought) when rainfall resumed and
climate was less dry compared to late spring/early summer (the period just before growth
cessation). Therefore, autumn wood (late-wood) may incorporate carbon fixed during the
summer drought period. This explains why in extremely dry years, despite the earlier growth
cessation due to summer drought, we still find a δ13C increase corresponding to
the severity of drought when complete tree-rings (early-wood plus late-wood) are
analyzed. Additionally, inter-annual δ18O in tree-rings declined (linked to very low
δ18O in early-wood), in contrast to the year by year rise in temperature. In wet
years, when pine growth extends into late spring/early summer, intra-annual δ18O in
tree-rings again declined, despite the seasonal temperature rise from spring to summer.
Thus, any evaporative enrichment of leaf water in the heavier isotope under drought
appears to be masked by the source water utilized for tree growth. Source water when
arriving from deeper moisture pools is less enriched in H218O compared to surface
water. Thus, as drought intensifies between years or within a year, pines seem to
use water less enriched in H218O from deeper soil layers. This water accumulates
from precipitation over a series of years and also appears to determine Δ13C and
tree growth, as both were best correlated with multiple years of past precipitation. |
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