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 />
system. In recent years, this steppe has been reported to be severely<br />
deteriorated because of heavy grazing (Chen and Wang, 2000). Heavy grazing<br />
accompanied with animal trampling normally has detrimental effects on soil<br />
properties (Greenwood and McKenzie, 2001; Zhao et al., 2007). Particularly in<br />
the topsoil, soil deformation is characterized by a decrease of pore volume and<br />
altered pore size distribution, which both affect water and air conductivities<br />
(Willat and Pullar, 1983; Krümmelbein et al., 2006), and soil water retention<br />
characteristics (Martinez and Zinck, 2004; Kutilek et al., 2006). The disturbance<br />
of soil structure also leads to lower water infiltrability and thus increases the risks<br />
for soil erosion and nutrient depletion. Therefore, these processes may cause a<br />
low water storage capacity and the loss of soil fertility, consequently decrease<br />
the grassland productivity (Christensen et al., 2004).<br />
Under the prevailing semi-arid climatic condition in Inner Mongolia, plant<br />
available water plays a key role for the sustainable development of steppe<br />
ecosystems. Therefore, it is necessary to <strong>und</strong>erstand the effects of grazing on<br />
water-related mechanisms and water budgets. Some studies have shown that<br />
grazing increases evaporation and decreases transpiration caused by an<br />
increase in bare gro<strong>und</strong> area and a decrease in biomass production (Bremer et<br />
al., 2001; Chen et al., 2007). However, to which extent grazing affects<br />
evapotranspiration and its partitioning into transpiration and evaporation is still<br />
unclear (Leenhardt et al., 1995). Another deficiency is that interception by the<br />
plant canopy and residue is normally ignored despite its potentially large<br />
contribution to the water budget. Moreover, it is widely recognized that the<br />
movement of water and heat is closely coupled, but their mutual interactions are<br />
rarely considered in practical applications (Saito et al., 2006). For instance, the<br />
effect of heat transport on water flow is often neglected mainly because of a lack<br />
of comprehensive data to fully parameterize coupled water and heat flow<br />
models.<br />
In this paper, a comprehensive dataset including soil, plant and<br />
meteorological measurements from the project “MAGIM” (Matter fluxes in<br />
grasslands of Inner Mongolia as influenced by stocking rate;<br />
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