85-14

The analysis on the relationship between the mean and the standard deviation of soil moisture show that: There is extremely significant correlation between the water contents in the soil of different time, no obvious differences between correlations of the 5 days (averages are 0.444 for 0~5cm layer and 0.499 for 5~10cm layer, r_{0.01}=0.354) or 4 years (0.514 and 0.454) intervals. Liner correlation coefficient is higher than the rank correlation coefficient. The standard deviation varies with the average. There are extremely significant correlation between the standard deviation and the mean of soil moisture for all 4 kind of soil. The correlation of a soil moisture profile between two time decreases with the increase of the interval, and reach a relative stable value (0.35 for clay loamy soil, 0.25 for grazed clay loamy soil) for the interval is over 35 days. The percent of positive correlation also decreases with the increase of the interval and reach about 80% for positive correlation and about 30% for extremely significantly positive correlation. The percent of positive correlation between two time of 1994 and 1999 are 96.3% and 85.2% respectively, and the extremely significantly positive correlation are 18.5% and 0 respectively. The percent of order stability of any two layer of the same profile in 1994 and 1999 are 40~96.9% and 22~93% respectively. These suggest that the water percent content in soil has some ratio variation, and the moisture of different point will vary with co-ratio, especially for the dry period and the deaquation process. The difference of soil moisture between two points will varies the same ratio as that of the mean. This is the main reason for the stability of spatial rank of soil moisture. But the stability of profile rank of soil moisture is a little lower than that of spatial rank.