SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Chapter 3 Factors controlling spatio-temporal variability of soil moisture using multivariate geostatistics
heterogeneity of soil moisture. As grazing intensity increased, animal trampling
and grazing decreased vegetation coverage and biomass, leading to increased
bulk density and decreased soil organic carbon. With heavy grazing this results
in a large proportion of bare soil and highly deteriorated soil properties. Under
such conditions, high evaporation and albedo are expected, leading to a trend
towards lower soil moisture and a more homogeneous moisture distribution at
the long-range scale.
To completely understand the controlling factors of soil moisture from these
data, several more considerations are needed. For example, correlations
derived from a single measurement, i.e. plant properties, normally omit seasonal
variations. Another deficiency is the lack information of soil moisture for deeper
soil, and potential shifts in sampling position and frequency. Although trends
between grazing intensity and soil moisture distribution were found, uncertainties
in the grazing gradient and its management history may have confounded the
results. Nevertheless, a conceptual model of the mechanistic controls on surface
soil moisture variability affected by grazing intensity could be derived.
4. Conclusions
In this paper we identified the main factors controlling the spatio-temporal
patterns of soil moisture as a function of grazing intensity in a semi-arid
grassland. Our results revealed that the variability of soil moisture was
characterized by weak to moderate spatial structures depending on sampling
time and grazing intensity. The spatial variance and, to a lesser extent, the
correlation length were found to be related to mean soil water content. The
correlation analysis showed that soil and plant properties, especially soil
physical properties that were impacted by grazing intensity, were important in
controlling the distribution of soil moisture. To adequately describe spatial
patterns of soil moisture, we need to consider the dependency of controlling
processes on the local conditions.
Using factorial kriging analysis, scale-dependency correlations between soil
moisture and its controlling factors were detected. The soil and plant properties
strongly controlled the variation of soil moisture in UG 99 at short-scale (90 m),
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