SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Keywords: Soil moisture; Grazing intensity; Inner Mongolia grassland;
Controlling factor; Scale-dependency
1. Introduction
Over-grazing has depleted vegetation coverage over large areas of
grassland in Inner Mongolia, leaving the exposed soil vulnerable to wind and
water erosion (Li et al., 2000; Gao et al., 2002). Recent research by Zhao et al.
(2007) found that heavy grazing in this region also degrades soil hydraulic and
mechanical properties. Based on studies in other regions, the degradation of
these soil properties could influence the spatio-temporal variation in soil
moisture (Williams et al., 2003; Hébrard et al., 2006). As a result, hydrological
processes governing plant water availability could greatly influence plant
stresses and hence heterogeneity in establishment caused by grazing (Evenari
et al., 1971).
The impact of grazing intensity, or other differences in land management, on
the spatio-temporal variability of soil moisture has been shown in previous
research to depend on numerous plant and soil factors (Hawley et al., 1983; Qiu
et al., 2001; Williams et al., 2003). However, these studies have reported
conflicting results, so there is a need for further research to examine the causes
of spatio-temporal variability in soil moisture under different land uses. As
grazing intensity, particularly on the grasslands of Inner Mongolia, has such a
large impact on hydrology, this area offers an ideal study site. Moreover, land
degradation in Inner Mongolia is recognised globally as a major problem
because of the local threat to agriculture and the wider impact on dust storms.
Understanding the factors controlling the spatio-temporal variability in soil
moisture will be essential in assessing the benefits of different land restoration
practices.
The patterns of soil moisture that develop are also fundamental to
physically-based hydrological models (Blöschl and Sivapalan, 1995; Giacomelli
et al., 1995; Western et al., 1999; Herbst and Diekkrüger, 2003). Several authors
have shown the characteristics of soil moisture variability, using spatial
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