Correlations Between Distribution Characteristics of Artemisia ordosica Root System and Soil Moisture Under Different ixation Stage of Sand Dunes

Water is the most important limiting factor to the arid and semiarid ecosystems, while the root system is the most important organ for plants to uptake soil moisture. In order to analyze the correlations between the distribution characteristics of Artemisia ordosica roots and soil moisture in different site conditions with different sand faxing status, A. ordosica plants were respectively selected from the fixed, semifixed and drifting sanddunes for the study in Mu Us sandy land. The distribution features of A. ordosica root systems on different plots were observed by sample collection at different soil depth, and the corresponding soil moisture was measured with TDR by layers. The results showed that the A. ordosica root systems contained most of coarse roots at the three types of sanddunes, followed by medium sized roots and with the least fine roots, and the biomass of the three kinds of roots was all decreased with the increment of soil depth in exponential way. The proportion of fine roots collected at 0-40 cm depth in the fixed, semifixed and drifting sanddune areas was 79.11%, 74.71% and 53.23%, respectively. A. ordosica plants grown in the fixed and semifixed sanddunes mainly utilized the soil moisture at 0-40cm depth, whereas the A. ordosica plants grown in the drifting sanddune could use more soil moisture below 40cm in depth. Along with the gradual increase of vegetation coverage from the drifting sanddunes to fixed sanddune types, more soil moisture was consumed. Meanwhile, the development of biological soil crusts on the surface of fixed sanddunes impeded the infiltration of precipitation, which led to the deterioration of soil moisture in the fixed sanddunes, which would finally cause the recession of A. ordosica in the fixed sanddunes in a long time run.