Spatial and Temporal Variability of Soil Moisture in the Typical Peak-cluster Depression Area of Northwest Guangxi

Zhang Ji-guang（Ecology）

Directed by:            Professor WU Jin-shui

        Professor SU Yi-rong

            Asso.Prof CHEN Hong-song

  Abstract

     The problems of poverty and environment degradation are the most serious both in southwest karst region and the Loess Plateau of China. Especially in the peak-cluster Depression area of karst region, the vertical hydrological process is well developed, the drought and waterlog is frequent, the contradiction between population and land is very serious, and the local environment is extremely fragile. As a result, soil moisture becomes the key factor for maintaining the structure and function of the degraded ecosystem. Based on geo-statistics and GIS techniques, temporal–spatial variability of surface soil moisture and its influencing factors were studied in a typical peak-clusterDepression of Guzhou village, an ecological migration area of northwest Guangxi. The results showed as follows:

（1）Soil moisture in Depression area had weak to middle variable characteristics in seasons. And it had obvious seasonal changes which were showed from the main parameters of the semi-variagrams on space. And its spatial variability was approximately opposite to the change of mean soil moisture.

（2）Different spatial and temporal structure and distributing pattern of soil moisture were showed at the Depression area. The characteristic of distributing pattern could be used to predict the probability of drought in dry season and waterlog in rainy season. The rainfall, land use type, altitude and SOC were significant factors influencing the variability of soil moisture.

（3）the soil moisture content was higher compared with the one in the Depression area Which would lead to the hill slope assarted by farmers. Soil moisture in hill slope had middle variable characteristics and its spatial variability had obvious changes with seasons. 

（4）land use type was an important influencing factor on the hill slope, The order of soil moisture content in different land use types were: Natural vegetation> abandoned lands > slope croplands > plantation. Other soil properties, such as SOC and total soil porosity were also had the same trend. So, as a measure for ecology restoration in the peak-cluster Depression area, natural restoration was better than plantation. 
 

Key words: karst; Peak-cluster Depression Area; Soil moisture; Spatial-temporal variability; Geo-statistics