By using data from pasture observation on agro-meteorology by weather stations of Qinghai Province

the charact eristics of so il moisture in native pasture are analyzed.Soil moisture increases from west to east

with slightly high values at the two boundaries from north to south.Soil moisture in the ten-day period of each year fluctuates in a "W" type.From 1989 to 2007

it declines obviously at the rate of 0.8%/ a.In the 0-20 cm soil layer

the rate is 0.25%/ a and in the 20-50 cm soil layer

0.04%/ a.The 0-50 cm soil profile may be divided into active layer(0-20 cm)

secondary active layer(20-40 cm)

and stable layer(40-50 cm).Soil water content decreases with soil depth under 520 mm precipit at ion and differs in different depths when precipitation is between 350 and 410 mm.In terms of the change tendency

the change of soil moisture in Xinghai County is not obvious.It has a slightly weak drop in Chu-ma-lai County and a weak drop in Henan

Gande

and Haibei Counties.The change tendency differs from its degree in different areas.Climate change is not only the direct cause of soil moisture reduction

but also the direct cause of pasture degra-dation.Soil moisture reduction is the main cause of pasture degradation.