The FLOWatch project: Measuring water,carbon dioxide and energy fluxes at the field scale
2006
For water, energy and CO2 fluxes in agricultural landscapes, the field scale plays a
crucial role since it corresponds to the scale at which humans directly influence
fluxes by managing the system for crop cultivation. This leads to a human-induced
spatio-temporal variability of these fluxes at the regional scale. Consequently, the
field scale is considered as the elementary scale for modelling of water, CO2 and
energy fluxes. Despite intensive research in the past, there is still a lack in
knowledge concerning the spatial and temporal interdependency of soil state variables
(e.g. moisture, soil temperature), matter fluxes from soil and vegetation (e.g.
water, carbon dioxide) as well as their variability and respective effective values
at the field scale. The FLOWatch project aims to improve our understanding of the
spatial and temporal variability of water, energy and carbon dynamics in the soil and
their role in determining effective evapotranspiration and carbon exchange fluxes at
the field scale. To this end, micrometeorological, geophysical and (ground-based)
remote sensing methods will be combined with mechanistic models describing the
dynamics of water, energy and CO2 in soils.
Modelling of C-dynamics involves the description of the turn-over of different
organic matter pools. The turnover rates depend on soil temperature, soil water
content, and soil CO2 concentration amongst others. Therefore, an accurate
representation of these state variables is a key issue for the predictive modelling
of carbon turnover and CO2 efflux. Within the FLOWatch project, several non-invasive
and soil physical methods to measure soil water content at different scales will be
implemented. At the point scale, far-field ground penetrating radar (GPR), electrical
resistivity tomography (ERT), and time domain reflectrometry (TDR) will be used. For
plot scale estimates of soil water content, a passive
L-band radiometer will be installed. To obtain a spatial representation of the energy
balance components, meteorological measurements will be combined with 2D soil surface
temperature images from an IR-camera. Spatial and temporal variability of CO2 fluxes
will be measured with automated soil CO2 flux systems (LICOR Biosciences). Temporal
variability of the CO2 flux at the plot scale will be measured using the eddy
covariance method when conditions allow it. For the modelling of the water balance,
the energy balance and the CO2 efflux, a model containing the following processes
will be used: (I) water and heat transport in variably saturated soils, (II) organic
carbon turnover based on with multiple pools with variable turnover rates, (III)
multiphase CO2 transport from the soil to the atmosphere.
In this presentation, the experimental setup, the modelling concept and the first
results of the FLOWatch project will be presented.
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