Responses of root water uptake to soil water dynamics for three revegetation species on the Loess Plateau of China

Abstract

AbstractIn water‐limited ecosystems, soil water regulates root water uptake (RWU) strategies. However, RWU responses to soil water changes under different species are not well‐understood. We assessed RWU responses of three revegetation species [shrub (Hippophae rhamnoides Linn.), coniferous forest [Platycladus orientalis (L.) Franco], and broad‐leaved forest (Robinia pseudoacacia L.) during the dry (May to June) and rainy (July to August) seasons in 2020 on the Loess Plateau using stable isotope methods. We sampled soil and xylem for each species at approximately weekly intervals and used the MixSIAR model to quantify RWU contribution with stable water isotopes. The results indicated that soil water in the shallow (0–40 cm) and middle (40–200 cm) soil layers fluctuated more strongly than the deep soil layer (200–300 cm) due to precipitation and evapotranspiration. Before precipitation in the dry season, most of the RWU for H. rhamnoides and R. pseudoacacia (97% and 98%) came from the middle layer under limited soil water. After precipitation in the dry season, the three species had similar RWU responses to soil water changes. After precipitation in the rainy season, the RWU change of H. rhamnoides and R. pseudoacacia with deep soil drying was more sensitive to soil water change than P. orientalis with sufficient deep water on August 3 and 11, while, the RWU of H. rhamnoides was more sensitive to soil water change than R. pseudoacacia on August 11 and 19. Thus, by switching its water‐use strategy, H. rhamnoides adapted better to the soil water environment than P. orientalis and R. pseudoacacia. This finding will help in selecting the optimal revegetation species for water use in a changing climate environment.