Regulations and patterns of soil moisture dynamics and their controlling factors in hilly regions of lower reaches of Yangtze River basin, China

YU Wei-qing(余蔚青)^{1, 2, 3}, WANG Yu-jie(王玉杰)^{1, 2}, HU Hai-bo(胡海波)⁴, WANG Yun-qi(王云琦)^{1, 2}, ZHANG Hui-lan(张会兰)^{1, 2}, WANG Bin(王彬)^{1, 2}, LIU Yong(刘勇)^{1, 2}

(1. School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China;
2. Key Laboratory of Soil and Water Conservation and Desertification Combating of Ministry of Education
(Beijing Forestry University), Beijing 100083, China;
3. Integrate Planning and Design Institute, China Aviation Planning and Design Institute (Group) Co. Ltd.,
Beijing 100120, China;
4. College of Forest Resources & Environment, Nanjing Forestry University, Nanjing 210037, China)

Abstract:Time-domain reflectometry was used to make continuous measurements of soil moisture to 18 sample points with depth of 2 m for 36 months in a typical artificial secondary oak forest located in a hilly area on Zijin Mountain in the suburbs of Nanjing, China. The data were then used to examine the patterns of soil moisture variations on temporal and spatial scales and predict the relationships between soil moisture and major factors of both meteorology and topography. Water in the topsoil was active, and the upper 30 cm of soil supplied about 43% of the water content variation during the whole year. This difference of water content changes among layers could be due to the distribution conditions of some soil physical properties. When initial soil moisture was in the range from 10% to 40%, the impact of a single storm event on soil moisture was extremely significant, especially on sunny slope. Both climate and slope condition were related to soil moisture change, and the impact of slope gradient on soil moisture was higher that on shady slope. Moreover, root uptake was another important path of soil water consumption.

Key words:soil moisture; precipitation; slope gradient; root distribution; soil water consumption