Abstract:Soil moisture is one of the most important factors in terrestrial ecosystems. Adequate knowledge of its spatio-temporal variability is critical to many scientific and practical applications. We explored the factors controlling moisture distribution in soils under typical land-use types (i.e., bamboo forest and tea garden) in a hilly region of Taihu Lake basin. In situ soil moisture measurements were made at different depths, and these were classified as dry or wet conditions, based on the precipitation during the previous 7 d. The main controlling factors were identified by using the classification and regression tree (CART) method. Canonical correspondence analysis (CCA) was then applied to quantitatively analyze the relationships between soil moisture and environmental factors under different land-uses at different soil depths. The results show that: (1) the relative influences of elevation, land use, and soil thickness on soil moisture distribution were larger than those of other environmental factors in most cases. Together these accounted for more than 50% of the total variation in soil moisture. However, their relative contributions differed between dry and wet conditions. (2) In dry conditions soil moisture was mainly affected by topographic indices such as elevation, slope, topographic wetness index (TWI) and profile curvature. Soil thickness and clay content also significantly affected soil moisture at 0-20 and 20-40 cm depths, respectively. The main factors controlling soil moisture in dry conditions varied with soil depth, but not with land-use type. This finding was different from that of a previous study, in which the study area had similar landforms and climatic conditions. This may be due to the effects of spatial scale. (3) In wet conditions, topographic indices and soil properties were the main factors controlling soil moisture in tea gardens at 0-20 and 20-40 cm depths, respectively. Both topographic indices and soil properties were the main controlling factors of soil moisture in a bamboo forest at these two depths. It is noted that the relationship between soil moisture and environmental factors at 20-40 cm depth is more complicated than that at 0-20 cm depth in bamboo forest. In contrast to dry conditions, both soil depth and land-use type had a significant impact on the environmental factors that control soil moisture distribution. This study is of great relevance to the sustainable utilization of water and soil resources and to the management of water and fertilizer in agriculture in this region.