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| Titel |
Seasonal and inter-annual dynamics in the stable oxygen isotope compositions of water pools in a temperate humid grassland ecosystem: results from MIBA sampling and MuSICA modelling |
| VerfasserIn |
Regina Hirl, Hans Schnyder, Karl Auerswald, Sylvia Vetter, Ulrike Ostler, Inga Schleip, Lisa Wingate, Jerome Ogee |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109407
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| Publikation (Nr.) |
 EGU/EGU2015-9312.pdf |
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| Zusammenfassung |
| The oxygen isotope composition (δ18O) of water in terrestrial ecosystems usually shows
strong and dynamic variations within and between the various compartments. These
variations originate from changes in the δ18O of water inputs (e.g. rain or water vapour) and
from 18O fractionation phenomena in the soil-plant-atmosphere continuum. Investigations of
δ18OÂin ecosystem water pools and of their main drivers can help us understand water
relations at plant, canopy or ecosystem scale and interpret δ18O signals in plant and animal
tissues as paleo-climate proxies.
During the vegetation periods of 2006 to 2012, soil, leaf and stem water as well as
atmospheric humidity, rain water and groundwater were sampled at bi-weekly intervals in a
temperate humid pasture of the Grünschwaige Grassland Research Station near Munich
(Germany). The sampling was performed following standardised MIBA (Moisture Isotopes
in the Biosphere and Atmosphere) protocols. Leaf water samples were prepared
from a mixture of co-dominant species in the plant community in order to obtain
a canopy-scale leaf water δ18O signal. All samples were then analysed for their
δ18OÂcompositions.
The measured δ18OÂof leaf, stem and soil water were then compared with the
δ18O signatures simulated by the process-based isotope-enabled ecosystem model MuSICA
(Multi-layer Simulator of the Interactions between a vegetation Canopy and the
Atmosphere). MuSICA integrates current mechanistic understanding of processes in the
soil-plant-atmosphere continuum. Hence, the comparison of modelled and measured data
allows the identification of gaps in current knowledge and of questions to be tackled in the
future.
Soil and plant characteristics for model parameterisation were derived from
investigations at the experimental site and supplemented by values from the literature.
Eddy-covariance measurements of ecosystem CO2 (GPP, NEE) and energy (H, LE)
fluxes and soil temperature data were used for model evaluation. The comparison of
measured and predicted ecosystem fluxes showed that the model captured the main
features of the diurnal cycles of GPP, NEE, LE and H, as well as the soil temperature
dynamics.
In this presentation I will present the main results of this model-data comparison, as well
as results from a model sensitivity analysis performed over a range of soil, plant and
meteorological parameters to evaluate the relative importance of each parameter on the
δ18O signatures of the various water pools. |
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