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| Titel |
Change in hydraulic properties and leaf traits in a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics |
| VerfasserIn |
B. Schuldt, C. Leuschner, V. Horna, G. Moser, M. Köhler, O. Straaten, H. Barus |
| 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. 8 ; Nr. 8, no. 8 (2011-08-12), S.2179-2194 |
| Datensatznummer |
250006078
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| Publikation (Nr.) |
 copernicus.org/bg-8-2179-2011.pdf |
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| Zusammenfassung |
A large-scale replicated throughfall exclusion experiment was conducted in a
pre-montane perhumid rainforest in Sulawesi (Indonesia) exposing the trees
for two years to pronounced soil desiccation. The lack of regularly
occurring dry periods and shallow rooting patterns distinguish this
experiment from similar experiments conducted in the Amazonian rainforest.
We tested the hypotheses that a tree's sun canopy is more affected by soil
drought than its shade crown, making tall trees particularly vulnerable even
under a perhumid climate, and that extended drought periods stimulate an
acclimation in the hydraulic system of the sun canopy. In the abundant and
tall tree species Castanopsis acuminatissima (Fagaceae),
we compared 31 morphological, anatomical,
hydraulic and chemical variables of leaves, branches and the stem together
with stem diameter growth between drought and control plots.
There was no evidence of canopy dieback. However, the drought treatment led
to a 30 % reduction in sapwood-specific hydraulic conductivity of sun
canopy branches, possibly caused by the formation of smaller vessels and/or
vessel filling by tyloses. Drought caused an increase in leaf size, but a
decrease in leaf number, and a reduction in foliar calcium content.
The δ13C and δ18O signatures of sun canopy leaves gave
no indication of a permanent down-regulation of stomatal conductance during
the drought, indicating that pre-senescent leaf shedding may have improved
the water status of the remaining leaves. Annual stem diameter growth
decreased during the drought, while the density of wood in the recently
produced xylem increased in both the stem and sun canopy branches
(marginally significant). The sun canopy showed a more pronounced drought
response than the shade crown indicating that tall trees with a large sun
canopy are more vulnerable to drought stress.
We conclude that the extended drought prompted a number of medium- to
long-term responses in the leaves, branches and the trunk, which may have
reduced drought susceptibility. However, unlike a natural drought, our
drought simulation experiment was carried out under conditions of high
humidity, which may have dampened drought induced damages. |
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