Abstract
Abstract. Soil moisture in deep soil layers is an important relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the spatial variations of deep soil moisture with respect to the topographic conditions has significant importance for vegetation restoration. In this study, we focused on analyzing the spatial variations and factors influencing soil moisture content (SMC) in shallow (0–2 m) and deep (2–8 m) soil layers, based on soil moisture observations in the Longtan watershed, Dingxi, Gansu province. The vegetation type of each sampling site for each comparison is same and varies by different positions, gradients, or aspects. The following discoveries were captured: (1) in comparison with shallow SMC, slope position and slope aspect may affect shallow soil moisture more than deep layers, while slope gradient affects both shallow and deep soil moisture significantly. This indicates that a great difference in deep soil hydrological processes between shallow and deep soil moisture remains that can be attributed to the introduced vegetation and topography. (2) A clear negative relationship exists between vegetation growth condition and deep soil moisture, which indicates that plants under different growing conditions may differ in consuming soil moisture, thus causing higher spatial variations in deep soil moisture. (3) The dynamic role of slope position and slope aspect on deep soil moisture has been changed due to large-scale plantation in semi-arid environment. Consequently, vegetation growth conditions and slope gradients may become the key factors dominating the spatial variations in deep soil moisture.
Highlights
In the semi-arid Loess Plateau of China, soil moisture is an important water source for plant growth in local ecosystems (Cao et al, 2009)
(2) A clear negative relationship exists between vegetation growth condition and deep soil moisture, which indicates that plants under different growing conditions may differ in consuming soil moisture, causing higher spatial variations in deep soil moisture
No significant difference in soil moisture content (SMC) was found between different slope positions in shallow layers, and the vegetation covers did not matter (Table 2)
Summary
In the semi-arid Loess Plateau of China, soil moisture is an important water source for plant growth in local ecosystems (Cao et al, 2009). This region is covered by nearly 100 m loess in thickness and a loose soil structure (Chen et al, 2007b), and the groundwater levels in this region are generally at depths of 30 m to 100 m below surface (Mu et al, 2003). Little of the groundwater at these depths can be used as a supply for soil evaporation and plant transpiration For this reason, plants in this area are forced to develop deep and robust root systems to utilize soil moisture stored in the deep soil layers (Chen et al, 2008a). Deep soil moisture (usually 2 m below surface) becomes especially important for the sustainable growth of plants in this area (Chen et al, 2008a; Y. Wang et al, 2011)
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