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| Titel |
Water balance measurements and simulations of maize plants on lysimeters |
| VerfasserIn |
Florian Heinlein, Christian Biernath, Christian Klein, Christoph Thieme, Eckart Priesack |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125199
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| Publikation (Nr.) |
 EGU/EGU2016-4746.pdf |
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| Zusammenfassung |
| In Central Europe expected major aspects of climate change are a shift of precipitation events
and amounts towards winter months, and the general increase of extreme weather events like
heat waves or summer droughts. This will lead to strongly changing regional water
availability and will have an impact on future crop growth, water use efficiency and yields.
Therefore, to estimate future crop yields by growth models accurate descriptions of
transpiration as part of the water balance is important.
In this study, maize was grown on weighing lysimeters (sowdate: 24 April 2013).
Transpiration was determined by sap flow measurement devices (ICT International Pty Ltd,
Australia) using the Heat-Ratio-Method: two temperature probes, 0.5 cm above and below a
heater, detect a heat pulse and its speed which allows the calculation of sap flow. Water
balance simulations were executed with different applications of the model framework
Expert-N. The same pedotransfer and hydraulic functions and the same modules to simulate
soil water flow, soil heat and nitrogen transport, nitrification, denitrification and
mineralization were used. Differences occur in the chosen potential evapotranspiration ETpot
(Penman-Monteith ASCE, Penman-Monteith FAO, Haude) and plant modules (SPASS,
CERES). In all simulations ETpot is separated into a soil and a plant part using the leaf are
index (LAI). In a next step, these parts are reduced by soil water availability. The sum of
these parts is the actual evapotranspiration ETact which is compared to the lysimeter
measurements.
The results were analyzed from Mid-August to Mid-September 2013. The measured sap
flow rates show clear diurnal cycles except on rainy days. The SPASS model is able to
simulate these diurnal cycles, overestimates the measurements on rainy days and at the
beginning of the analyzed period, and underestimates transpiration on the other days. The
main reason is an overestimation of potential transpiration Tpot due to too high simulated
leaf area indexes (LAIs) at the beginning of the analyzed period. At the end of
the measurement period, green LAI decreases and thus Tpot gets lower. At daily
time steps transpiration simulated by SPASS agrees well with the measurements
while CERES simulations overestimate Tact. Differences in ETact simulations
compared to the lysimeter measurements mainly occur due to the different choice of
ETpot-models.
In conclusion, with the help of canopy models the water balance of the lysimeter system
can be reasonably well simulated. However, the applied crop models oversimplify
plant water transport and thus may not describe the water uptake and hence crop
growth dynamics well enough for application of expected future climate scenarios. |
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