SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
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Chapter 5 Modeling Grazing Effects on Coupled Water and Heat Fluxes in Inner Mongolia Grassland<br />
the ungrazed sites, the grazed sites generally have lower soil water storage. In<br />
August, the driest soil conditions occur at HG, where water contents approach<br />
the permanent wilting point due to both strong evaporation losses and low water<br />
storage in the subsoil. In contrast to this, rainfall water can percolate into deeper<br />
soil layers (>40 cm) in the two ungrazed sites. At the topsoil (e.g., 20 cm), UG 79<br />
is drier than UG 99 probably due to higher water withdrawal at the more<br />
productive site UG 79.<br />
Soil temperature shows typical changes with diurnal weather condition (Fig.<br />
2). With increasing soil depth, soil temperature decreases, indicating energy<br />
transfer from the topsoil to the subsoil during the growing period. With increasing<br />
grazing intensity, soil temperature is higher, especially in the topsoil. In general,<br />
soils seem to warm up or cool down quicker in the grazed sites than the<br />
ungrazed sites. However, compared to the other sites, the soil in HG seems to<br />
buffer the abrupt drop in temperature as early autumn snow occurred on 7<br />
September, which might relate to the higher soil temperature and the lower heat<br />
conductivity of the drier soil at HG.<br />
a<br />
b<br />
Soil depth (cm)<br />
c<br />
d<br />
-20<br />
-40<br />
-20<br />
-40<br />
0<br />
-20<br />
-40<br />
0<br />
-20<br />
-40<br />
0<br />
0<br />
0<br />
20-May 9-Jun 29-Jun 19-Jul 8-Aug 28-Aug 17-Sep<br />
Time (days)<br />
0.25<br />
0.21<br />
0.17<br />
0.15<br />
0.13<br />
0.11<br />
0.09<br />
0.07<br />
0.05<br />
Soil moisture (cm 3 cm -3 )<br />
a<br />
b<br />
Soil depth (cm)<br />
c<br />
d<br />
-20<br />
-40<br />
0<br />
0<br />
0<br />
-20<br />
-40<br />
0<br />
-20<br />
-40<br />
0<br />
-20<br />
-40<br />
20-May 9-Jun 29-Jun 19-Jul 8-Aug 28-Aug 17-Sep<br />
Time (days)<br />
Fig. 5.2. Contour plots of soil moisture (left side) and soil temperature (right side) for the<br />
four grazing intensities from May to Sept. 2006 (a is UG 79, b is UG 99, c is WG, and d is<br />
HG).<br />
Model Calibration and Validation<br />
25<br />
22<br />
19<br />
16<br />
13<br />
10<br />
7<br />
4<br />
1<br />
Soil temperature ( 0 C)<br />
97