SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

thus grassland productivity.
Keywords: Grazing intensity; Spatial variability; Geostatistics; Soil properties;
Correlations
1. Introduction
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Inner Mongolia grassland has been severely deteriorated in recent years
because of inappropriate management, that resulted in an increasing
degradation of the vegetation cover followed by pronounced soil erosion and
nutrient depletion (Li et al., 2000). These processes may cause low water
storage capacity and loss of soil fertility, consequently decrease the grassland
productivity. Therefore, to develop sustainable management strategies, the
processes emerging from pasture degradation by grazing are urgent to be
understood as they play a key role in the ecosystem stability.
Grazing associated with animal activity altered hydraulic and mechanical
soil properties. Greenwood et al. (1997) found significant differences in
unsaturated hydraulic conductivity, soil strength and bulk density for the surface
soil between ungrazed and grazed pastures. Warren et al. (1986) reported that
trampling animals caused soil deformation by exerting high ground contact
pressures under their hooves. Besides soil compression, shear stresses further
destroy soil structure by kneading and homogenization, which mainly related to
a change of macroporosity and the connectivity of the pore system. Destruction
of soil structure was observed for sheep grazing (Proffitt et al., 1995), cattle
trampling (Pietola et al., 2005), and reindeer herding (Peth et al., 2003). Such
changes depend not only on the magnitude of applied stresses, but also on the
soil moisture controlled aggregate stability at the time of trampling (Horn and
Fleige, 2003; Richard et al., 2001). Furthermore, animal trampling is mostly not
static but must be considered as a short time dynamic process, where the soil
undergoes repeated sequences of loading, unloading and reloading events
(Peth and Horn, 2006). This dynamic soil compression is more intense due to a
pronounced inter-particle shear deformation compared to the compaction under
static loading. Finally, this will result in an intensive reduction of soil infiltrability