SOIL MOISTURE DYNAMIC OF ARTEMISIA ORDOSICA COMMUNITY AND ITS RELATIONSHIP WITH PLANT ROOTS AT DIFFERENT SUCCESSION STAGES IN MU US SANDY LAND

For a thorough analysis soil moisture dynamics in different fixed degree (shifting sandy land, semi-fixed sandy land and fixed sandy land) of Artemisia Ordosica samples in Mu Us sandy land, we used AR-5 soil moisture automatic monitoring system for a long-term and continuous monitoring of soil moisture in this study, and a new rainfall sensor monitoring system named AV-3665R was also used to monitor the precipitation. The results showed: (1) in the study area, the seasonal variation degree of soil moisture and precipitation was basically in synchronization, the soil water content was significantly correlated with precipitation. Under the influence of precipitation, root system and evapotranspiration, there were differences in soil moisture dynamics in three samples with different fixed degrees. The soil water content in fixed sandy land was significantly less than that in semi-fixed sandy land and shifting sandy land in different soil layers. (2) The change of soil water content was divided into three periods every year. After increasing steadily in November to February, the soil water content increased significantly in March, and then decreased slowly in April to June. The soil water content was significantly increasing in July to October. (3) In non-precipitation days, the overall trend of soil water content in 0-100 cm soil layer was to decrease gradually. The daily minimum soil water content occurred at 16:00, and then rebounded after 20:00. The soil water potential in 20 cm soil layer was the highest, and it was the source of soil water when the evaporation was strong, which can adjust the direction of soil moisture movement. (4) The vertical distribution of soil water content can be divided into four layers: the soil moisture upheaval layer (0-10 cm), soil moisture sensitive layer (10-40 cm), soil water active layer (40-120 cm) and soil moisture stable layer (120-200 cm). (5) Fine roots accounted for the highest proportion in fixed sandy land, the lowest in shifting sandy land, and the opposite of rough roots. There was no significant change in the percentage of root biomass of different diameters in each soil layer, and they were all close to the average level of the entire root distribution layer. The regression equations of the root biomass of each of the three types of plots with soil depth are exponentially distributed, and the relationship is y=ae(-bx) (a and b are positive numbers), and the decline trend of fine root biomass is the most obvious. (6)With the increase of vegetation coverage, soil bulk density showed a downward trend, soil water holding capacity showed an upward trend, and this change mainly occurred in the root layers.