SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Chapter 5 Modeling Grazing Effects on Coupled Water and Heat Fluxes in Inner Mongolia Grassland
the ungrazed sites, the grazed sites generally have lower soil water storage. In
August, the driest soil conditions occur at HG, where water contents approach
the permanent wilting point due to both strong evaporation losses and low water
storage in the subsoil. In contrast to this, rainfall water can percolate into deeper
soil layers (>40 cm) in the two ungrazed sites. At the topsoil (e.g., 20 cm), UG 79
is drier than UG 99 probably due to higher water withdrawal at the more
productive site UG 79.
Soil temperature shows typical changes with diurnal weather condition (Fig.
2). With increasing soil depth, soil temperature decreases, indicating energy
transfer from the topsoil to the subsoil during the growing period. With increasing
grazing intensity, soil temperature is higher, especially in the topsoil. In general,
soils seem to warm up or cool down quicker in the grazed sites than the
ungrazed sites. However, compared to the other sites, the soil in HG seems to
buffer the abrupt drop in temperature as early autumn snow occurred on 7
September, which might relate to the higher soil temperature and the lower heat
conductivity of the drier soil at HG.
a
b
Soil depth (cm)
c
d
-20
-40
-20
-40
0
-20
-40
0
-20
-40
0
0
0
20-May 9-Jun 29-Jun 19-Jul 8-Aug 28-Aug 17-Sep
Time (days)
0.25
0.21
0.17
0.15
0.13
0.11
0.09
0.07
0.05
Soil moisture (cm 3 cm -3 )
a
b
Soil depth (cm)
c
d
-20
-40
0
0
0
-20
-40
0
-20
-40
0
-20
-40
20-May 9-Jun 29-Jun 19-Jul 8-Aug 28-Aug 17-Sep
Time (days)
Fig. 5.2. Contour plots of soil moisture (left side) and soil temperature (right side) for the
four grazing intensities from May to Sept. 2006 (a is UG 79, b is UG 99, c is WG, and d is
HG).
Model Calibration and Validation
25
22
19
16
13
10
7
4
1
Soil temperature ( 0 C)
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