Variation of soil water in Caragana microphylla woodlands with runoff-gathering project, Gansu of northwestern China

Low precipitation is the major constraint for plant growth in the semi-arid region of Loess plateau in China. Runoff regulation has been proved to be a promising approach to increase the utilization of precipitation and local water supply. The objective of this study was to investigate the soil water and plant growth conditions in Dingxi semi-arid area 14 years after applying runoff regulation project on slope- separated flat terraces (SSFT) in the years with maximum or minimum rainfall. The results showed that in the long-term drought conditions, there were regular changes for the soil moisture content in the different areas of the SSFT, control area, slope-separated and flat terraces, soil moisture higher in control area than in slope-separated flat area, and higher in flat area than in slope-separated area, however the differences were insignificant. Under the condition of continuous drought, soil water in both of Caragana microphylla woodland and control area was in lower level with average soil moisture only 5%. It is true that runoff regulation project could effectively control soil and water loss, increase soil water in C. microphylla woodland, improve water supply to the grass and wood growth. However, the C. microrphylla suffered from the low and insufficient soil water supply under the long-term dry climatic condition in this region. In the future there is a need to increase the water-gathering percentage in designing runoff regulation project and enhance the maintenance of the engineering practices.