The Temporal Characteristics Of Soil Moisture On Typical Steppe Of The Inner Mongolia Plateau

The highly spatial and temporal variability and correlation of soil moisture leads to the scale effect on the accurate measure and predication of soil moisture. Systematic study on the spatial and temporal variable feature of soil moisture, especially on the temporal feature of spatial variation and the spatial feature of temporal variation is helpful for the establishment of measuring method and predication model.This is a study on the variation and trend of soil moisture and the climate, and the autocorrelation nature of soil moisture based on the data of climate of Baiyinxile region and the data of observation on the several typical soils of the semi-arid region for over 20 years. Based on this, this study has analyzed the temporal nature, the temporal feature of spatial variation and the spatial feature of temporal variation of moisture in these soils. The following is the main result.1. There are very high correlationship between the soil moisture dynamic of different spatial points; between spatial soil moisture of different time; between the soil moisture in a profile of different time; between the different profiles at the same time; and so on suggest that in the 4 dimensional time-space, the rank or distribution pattern of soil moisture in any one or several dimension is stable in any other dimension.2. The ratio of soil moisture between two times is approximate for different spatial points. The standard deviation relates with the mean and SD~M points are distributing in a triangle region suggest that the soil water content will vary proportionally after being disturbed by rain or evapotranspiration, and the soil moisture of different points will vary with co-ratio when they are in the same environment and the same disturbance history. The difference of soil moisture of two points will vary with the mean.3. The soil moisture has very high autocorrelation and the correlation coefficient increases with the increase of soil depth, but decrease with the increase of lag time. The correlation coefficient of yearly normalized soil water content is decreased, especially for the deep layer soil. The positive correlated lag time of normalized soil water content is short than 45 days. And there is a negative correlationship when the lag time is about 60 days. These suggest that the direct determination effect of soil moisture on later soil water content is not long than 45 days, and there may be a negative feed back effect on the soil water content of about 60 days later. The approximation of soil water content at two times of over 90 days interval of a year may be the main contributor and the small trend may be the minor to the long time correlation.4. The soil moisture in deeper layer of grazing and ungrazing grassland is the same for most of the growth season suggest that evaporation from the soil surface has a very intensive effect on the soil moisture and that the soil of this area has a very well developed capillary pore. It is very important to increase the vegetation coverage for the using of the limited water resource.5. Grazing can greatly decrease the soil moisture in the 0~20cm layer especially the...