SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Differences in soil temperature simulations by different model approaches
are not as apparent as soil moisture simulations. All simulated temperatures
match well with the measured values (Fig. 7), suggesting that the effects of
hydraulic parameters on heat transfer are not present. The model
underestimates soil temperature at 5 cm depth, which might be associated with
the overestimation of heat conductivity in the topsoil. Heat flux into deeper soil
layers is predicted well even at steep gradients like on 7 Sept. 2006, indicating
that HYDRUS is also able to display heat transport in soils under abruptly
changed boundary conditions.
Soil temperature ( o C)
30
20
10
0
30
20
10
0
30
20
10
0
5 cm
18-Jun-05
20 cm
07-Aug-05 26-Sep-05 05-Jun-06 25-Jul-06 13-Sep-06
18-Jun-05 07-Aug-05 26-Sep-05 05-Jun-06 25-Jul-06 13-Sep-06
40 cm
Measured LDP NN Inverse
18-Jun-05 07-Aug-05 26-Sep-05 05-Jun-06 25-Jul-06 13-Sep-06
Time (days)
Fig. 5.7. Soil temperature comparison between measured and simulated results in UG
79 during the growing period in 2005-2006. LDP: Laboratory-derived hydraulic
parameters, NN: neural network, and Inverse: inverse model.
Soil Water and Heat Fluxes
After model calibration and validation soil water and heat fluxes, and water
budget components are calculated from the LDP models for the four sites during
the growing periods of 2004-2006. Despite identical net radiation are assumed
for each site, daily soil heat fluxes increase with increase of grazing intensity (Fig.
8), suggesting that partitioning of the surface energy is influenced by a change in
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