Effect of Artificial Caragana korshinskii Forest on Soil Water in the Semiarid Area of Loess Hilly Region Study on introduction and breeding of improved breeds of seabuckthorn in the semiarid loess hilly region Stomatal conductance and influence factors of seabuckthorn in Loess Hilly Region Study on the characteristics of water physiological ecology of seabuckthorn and the communities in the semiarid loess hilly region