[Spatial and temporal characteristics of soil moisture dynamics in Loess Plateau]

Field monitoring results of wasteland soil water content of during growing season of seven years in Zhuanyaogou valley of northwestern Shanxi Province, and the results showed that the seasonal dynamics of the soil water was controlled by annual precipitation and its distribution. The seasonal dynamics of soil water in a normal rainfall year could be divided into three stages, i.e., consumption stage from late spring to early summer, storage stage from late summer to early autumn, and second consumption stage from late autumn to early winter. The relationship equation between soil water content and measuring number was linear (1988, 1990), exponent (1992, 1995) and parabola curve (1993). The vertical profiles of soil water in the wasteland in different rainfall year were different, and the soil water content increased with increasing depth. The equations between soil water content and soil depth in all years were cubic. Taking 150 cm as a boundary, the ratio of soil water content in lower layers to upper layers was larger than 1, and the variance coefficient of soil water decreased with increasing depth. The soil water profile in 0-300 cm depth for seven year's average could be divided into three layers, i.e., active layer (above 200 cm), transitive layer (between 200-250 cm) and stable layer (below 250 cm), and the depth of each layer varied with the annual precipitation and its distribution. The ANOVA result of soil water content in extremely high rainfall showed a great difference with that in other years. The difference between soil water content in wasteland and in Caragana korshinskii plantation was significant, but was not different from that in Populus hopeiensis and Populus simonii plantation respectively. The quantitative analysis methods used in this paper facilitated the comparison of soil moisture in different region and in different vegetation.