SOIL-WATER AND TEMPERATURE PATTERNS IN AN ARID DESERT DUNE SAND

Under arid natural conditions, soil water content governs and limits t he number and size of perennial plant species. Thus, plant-available s oil water is the main constraint for sustainable control of desert enc roachment. To evaluate possibilities for re-vegetation of bare sand su rfaces, soil water and temperature patterns for typical sand dunes in a desert climate were investigated. Bare and vegetated soil transects were selected for observation of soil water content and temperature. T he investigated soil transects covered crest-to-crest spacings (about 60 m horizontally and 15 m vertically) in a shifting sand dune area. O bservations were made at Shapotou field research station bordering the Tengger Desert in Northwestern China. The paper presents two-dimensio nal properties of soil water content (0.1-3.0 m depth) and temperature (0-1.0 m depth) before and after rainfall. Rainfall (15-22 mm) affect ed soil water distribution down to 1.5-2.0 m and temperature distribut ion down to 1.0 m. Soil water appeared to be transported through the a pparently highly pervious and homogeneous sand along the dune slopes. High water contents and, thus, infiltration occurred mainly at the non -sloping parts, i.e. the dune crests and bottoms. Rainfall changed the temperature patterns from a mainly horizontally layered appearance be fore the rainfall to increasingly vertically shaped patterns.