SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Chapter 5 Modeling Grazing Effects on Coupled Water and Heat Fluxes in Inner Mongolia Grassland
The decrease in soil water storage and the low drainage indicate that
infiltrated water is mostly consumed by ET within a single growing period (Table
5). Note that in a dry year (2005) ET decreases by 40% compared to a wet year
(2004) due to water deficiency. This is in line with large differences between
reference ET and Pan-evaporation in 2005, but minor differences between them
in 2004 (Fig. 10). Differences in Tp related to grazing are also less pronounced
in the wetter years (2004 and 2006) than in the drier year (2005), indicating the
restriction on plant water uptake by low water availability under dry conditions.
Evapotranspiration (mm)
20
15
10
5
0
20
15
10
5
0
20
15
10
5
0
ET FAO ET Pan ET Act
25-May-06 19-Jun-06 14-Jul-06 08-Aug-06 02-Sep-06 27-Sep-06
25-May-05 19-Jun-05 14-Jul-05 08-Aug-05 02-Sep-05 27-Sep-05
25-May-04 19-Jun-04 14-Jul-04 08-Aug-04 02-Sep-04 27-Sep-04
Time (days)
Fig. 5.10. Evapotranspiration comparison from three methods in UG 79 during the
growing period in 2004-2006 (ETFAO: FAO, ETPan: Pan evaporation, and ETAct: Modelled
ET).
DISCUSSION
Grazing Effects on Soil Properties and Model Validation
Our results showed a decrease of total- and macro- pore volume and an
increase of meso-pore volume as a result of grazing. This was in agreement with
Villamil et al. (2001), who proofed a change of water retention characteristics by
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