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| Titel |
Crop evapotranspiration partitioning and comparison of different water use efficiency approaches |
| VerfasserIn |
Pierre Béziat, Vincent Rivalland, Nathalie Jarosz, Eric Ceschia, Gilles Boulet, Pierre Gentine |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034426
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| Zusammenfassung |
| In the context of climate change and water resource limitations for agriculture,
agro-ecosystems water use efficiency (WUE) assessment and improvement is essential. The
principal aims of this study are 1) to assess the different components of the agro-ecosystem
water budget and 2) to analyse and compare the WUE calculated for plants (WUEplt), for
the ecosystem (WUEeco) and from an agronomical point of view (WUEagro) for
several crops during the growing season and at the annual time scale, as well as to
evaluate the environmental impact of crop rotations and intercrop on WUEeco and
WUEagro.
To achieve this goal, EC measurements of CO2 and water fluxes were performed above
winter wheat, maize and sunflower at Auradé and Lamasquère sites in south west France. To
infer WUEplt, an estimation of plant transpiration (TR) is needed, therefore a new
methodology of ETR partitioning between soil evaporation (E) and TR based on marginal
distribution sampling (MDS) was tested and evaluated against the ICARE-SVAT double
source mechanistic model.
Results showed good agreement between both partitioning methods and MDS proved to
be a convenient and robust tool with reasonable associated uncertainties for estimating E.
During the growing season, the proportion of E in ETR was around one third, varying mainly
with crop leaf area. When calculated at the annual time scale, the proportion of E
in ETR reached more than 50Â %, depending on both crop leaf area and bare soil
duration and distribution within the year. WUEplt values ranged between -4.3Â g C
kg-1 H2O for maize and -5.8 g C kg-1 H2O for winter wheat. It was strongly
dependant on meteorological conditions (mainly vapour pressure deficit) at both daily
and seasonal time scale. When normalised by vapour pressure deficit to reduce
the effect of climatic variability on WUEplt, maize (C4 photosynthesis crop) had
the highest efficiency. WUE values were lower at the ecosystem level than at the
plant level because of water loss through E and carbon release through ecosystem
respiration. This observation was even more pronounced at the annual time scale
because bare soil periods were included in the calculation. To account for carbon
input through organic fertilisation and output through biomass exportation during
harvest, net biome production (NBP) was considered in the calculation of ecosystem
WUE (WUENBP). This environmental WUE consideration markedly decreased the
efficiency of the ecosystem, especially for crops with important carbon exports as
observed for the maize used for silaging at Lamasquère during the year 2005-2006.
Finally, the environmental and the agronomical WUE approaches were compared and
discussed considering the different processes accounted for by both considerations. |
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