SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Chapter 2 Spatial variability of soil properties affected by grazing intensity in Inner Mongolia grassland
WDPT related with SOC and SWC.
The organic matter deriving from roots and foliage might additionally
contribute to the hydrophobicity by releasing aliphatic compounds (Rumpel et al.,
1998). The significant positive relationship between WDPT and SOC (r = 0.79**)
(Table 9 and Fig. 4c) suggested that the organic substance reduced the rate of
wetting (Peng et al., 2003). Furthermore, the results also confirmed a positive
relationship between WDPT and SWC (r = 0.52**), indicating the occurrence of
water repellency was closely related with the water content which in itself might
be influenced by SOC concentration (“critical SWC”, Dekker et al., 2001; Täumer
et al., 2005). These results underlined the interaction of bio-hydrological
processes that a high SOC concentration reduced water infiltration through
increasing water repellency, but also limited water evaporation through the
organic litter mulch by which more water was retained in the soil.
SS related with Soil texture, SWC and BD, SOC.
SS was positively related with sand content (r = 0.78**) and BD (r = 0.48**,
Table 9 and Fig. 4d), while it was negatively related with silt content (r = -0.80**),
SOC (r = -0.32*), and SWC (r = -0.77**), respectively. However, no clear
correlation with SWC was found for the shear vane tests in each plot, which
might be explained by the high variance of SS within each plot at nearly identical
values of SWC. This indicated that the mechanical properties were more related
with soil texture than with the hydraulic properties. The compaction effects of
animal trampling (land use) were mainly determined by the soil types. Willat and
Pullar (1984) postulate structural damages by sheep hoof pressures leading to
increased bulk density and a decrease in total pore volume in Australian silty
loam soils. We suggest that an increase in bulk density, reduced macropores,
and in combination with high hoof pressures leads to compacted topsoil.
Multiple regression analysis among the soil properties.
By multiple stepwise regression analysis for selected eight soil parameters
following pedotransfer functions (PTFs) showing very significant
interrelationships were derived:
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