Depth and Amount of Deep Soil Water Consumption in Ecological Forests on the Loess Plateau

  Objective  It is important to clarify the water consumption pattern of ecological forests in Loess Plateau for water resources management. However, it is limited to the sampling depth, and there is a lack of research on the depth and amount of maximum water consumption for ecological forests.

  Method  Three common ecological forest species of Loess Plateau, namely, 16-year-old Platycladus orientalis, Hippophae rhamnoides, and Robinia pseudoacacia in Yan'an, were selected. Soil water contents under different ecological forests and natural grassland were obtained by hand-made auger. Firstly, the active soil water layer of the ecological forests was determined based on the annual seasonal soil water content change. Secondly, the water consumption depth and amount of the three ecological forests were determined based on the soil water contents in the soil depth profile( >25 m) compared with grassland. Finally, the rate of water consumption of ecological forests from different soil layers was analyzed.

  Result  The active soil water layer was considered in 2 m depth through seasonal soil water changes in Yan’an area. The more water consumption depths were 12.0 m, 12.2 m and 23.2 m with the water consumption amounts of 269 mm, 664 mm and 1727 mm for Platycladus orientalis, Hippophae rhamnoides, and Robinia pseudoacacia, respectively. The deep soil water consumption rate of Robinia pseudoacacia was the highest, which was 108 mm yr⁻¹, followed by Hippophae rhamnoides (42 mm a⁻¹) and Platycladus orientalis (17 mm a⁻¹). The water consumption amount from the 2-10 m soil layer of Robinia pseudoacacia only accounted for 45% of the total water consumption.

  Conclusion  We need to select the appropriate sampling depth of soil layer according to the water consumption characteristics of ecological forest species.