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| Titel |
Transpiration in an oil palm landscape: effects of palm age |
| VerfasserIn |
A. Röll, F. Niu, A. Meijide, A. Hardanto, Hendrayanto, A. Knohl, D. Hölscher |
| 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 ; 12, no. 19 ; Nr. 12, no. 19 (2015-10-05), S.5619-5633 |
| Datensatznummer |
250118110
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| Publikation (Nr.) |
 copernicus.org/bg-12-5619-2015.pdf |
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| Zusammenfassung |
| Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas
of humid tropical lowlands. Landscapes dominated by oil palms usually
consist of a mosaic of mono-cultural, homogeneous stands of varying age,
which may be heterogeneous in their water use characteristics. However,
studies on the water use characteristics of oil palms are still at an early
stage and there is a lack of knowledge on how oil palm expansion will affect
the major components of the hydrological cycle. To provide first insights
into hydrological landscape-level consequences of oil palm cultivation, we
derived transpiration rates of oil palms in stands of varying age, estimated
the contribution of palm transpiration to evapotranspiration, and analyzed
the influence of fluctuations in environmental variables on oil palm water
use. We studied 15 two- to 25-year old stands in the lowlands of Jambi,
Indonesia. A sap flux technique with an oil palm specific calibration and
sampling scheme was used to derive leaf-, palm- and stand-level water use
rates in all stands under comparable environmental conditions. Additionally,
in a two- and a 12-year old stand, eddy covariance measurements were
conducted to derive evapotranspiration rates. Water use rates per leaf and
palm increased 5-fold from an age of 2 years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible,
but less pronounced, for estimated stand transpiration rates of oil palms;
they varied 12-fold, from 0.2 mm day−1 in a 2-year old to
2.5 mm day−1 in a 12-year old stand, showing particularly high variability in
transpiration rates among medium-aged stands. Comparing sap flux and
eddy-covariance derived water fluxes suggests that transpiration contributed
8 % to evapotranspiration in the 2-year old stand and 53 % in the
12-year old stand, indicating variable and substantial additional sources of
evaporation, e.g., from the soil, the ground vegetation and from trunk
epiphytes. Diurnally, oil palm transpiration rates were characterized by an
early peak between 10 and 11 a.m.; there was a pronounced hysteresis in the
leaf water use response to changes in vapor pressure deficit for all palms
of advanced age. On the day-to-day basis this resulted in a relatively low
variability of oil palm water use regardless of fluctuations in vapor
pressure deficit and radiation. We conclude that oil palm dominated
landscapes show some spatial variations in (evapo)transpiration rates, e.g.,
due to varying age-structures, but that the temporal variability of oil palm
transpiration is rather low. The stand transpiration of some of the studied
oil palm stands was as high or even higher than values reported for
different tropical forests, indicating a high water use of oil palms under
yet to be explained site or management conditions. Our study provides first
insights into the eco-hydrological characteristics of oil palms as well as a
first estimate of oil palm water use across a gradient of plantation age. It
sheds first light on some of the hydrological consequences of the continuing
expansion of oil palm plantations. |
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