Abstract: The characteristics of root system distribution play a crucial role in root water uptake simulation and the flow dynamic in vadose zone with vegetation in semiarid regions.The linear and simple nonlinear root density distribution models were adopted frequently in the previous researches and most root water uptake models depended on the root system density distribution closely.In order to depict the real Artemisia ordosica root system density distribution and its relationship with soil water content,the root biomass and rhizospheric soil moisture were obtained by mining Artemisia ordosica roots integrally and were analyzed using the concept of plant crown level and static age level in this study.The results indicated that the Artemisia ordosica roots system is in accordance with lognormal distribution,and the uniform root density distribution can not only ignore the difference among Artemisia ordosica individuals,but also is of universal applicability.When there is a persistent drought,the reduced root water uptake in shallow root zone by water stress could be compensated by the root water uptake in deep root zone where it is relatively moist.Therefore,the complex biophysics indicates that the root water uptake is not only related to the root system density distribution,but also depends on the water state in vadose zone.

Key words: semiarid region, Artemisia ordosica, age class, distribution of rootsystem