Soil moisture dynamic of natural meadow and its impacts on forage biomass in Qinghai Lake region

The dynamic changes of soil moisture on natural grassland and the relations between forage biomass and the soil moisture in Qinghai Lake region were analyzed. Results indicated that changes of the soil humidity in the Qinghai Lake region can be divided into four periods, such as the slowly lost period in spring, the slowmoving convalescent period in the end of spring and early summer, the fastly lost period in summer and the fast increment and imbursement period in autumn. The perpendicular variety of the soil moisture differed among different years. 0-30 cm depth of soil moisture levels effected by factors such as weather and pasture growth, and the impact of wet and dry changed significantly, the changes in 30-50 cm depth of soil moisture levels were relatively stable．The forage biomass at the end of each month during the growth season (from May to September) was closely related to the soil humidity in its front period. The influence of the soil humidity in previous year on forage biomass was more obvious in the early period of forage grass growth, and it worn off gradually in late period.