Characteristics Of Soil Aggregation Stability And Its Spatial Variability In The Small Watershed Of South Hunan Province

It is easy to form the natural disasters of debris flow, landslides, mountain floods and other during rainstorms at Leishui watershed. Especially in 2006, the great geological disasters caused large economic losses when "Bilis" strong storm attacked on. Therefore, it was the practical importance to study on characteristics of soil aggregate stability and soil corrosion resistance in this aera. The characteristics of soil aggregate stability, soil corrosion resistance and theirs spatial variability were sydied in Guangqiao river small watershed that is the first tributary of Leishui. The main rearch results were follow as:1. The content distribution of the different size soil particle revealed the normal distribution and its variation coefficient (CV) was between 32.5% and 67.1% at Guangqiao river small watershed. The content order of the coarse sands was wasteland>gardens >woodland>vegetable fields>paddy fields>upland, that of the medium-fine Sand was gardens>vegetable fields>upland>paddy fields>wasteland>woodland, that of silt was dryland>vegetable fields>paddy fields>woodland>wasteland>gardens and that of. Clay was woodland>gardens>dryland>paddy fields>vegeTab fields>wasteland under different land utilization patterns.2. Generally, the CV of soil aggregate stability indicator varied between 22.9% to 44.1%, it belonged to from medium to weak level.As regards spatial variation, except soil aggregation statu was the stronger relation,while its correlation coefficent was less than 25%, that of the remaining three indicators varied between 44.2% to 67.6%, while they were all a moderate spatial correlation. The positively correlation was observed between the content of more than 0.25mm water stable aggregation and that of organic matter. If the range of pH value was from 5.0 to 7.0, its effect on aggregation stability was much small, while that of pH value was not the above range, its has some influence on the soil aggregation stability could be found.3. The spatial interpolation map showed that the radation characteristics from the center to surrounding of the destruction rate on more than 2mm aggregation was from weak to stronger, the spatial characteristics of on more than 1mm aggregation was the stronger of west-east position and the weaker of the middle section, the patches chaeracter that was overall sronger the south than the north was found in more than 0.5mm aggregation, and the character of the destruction rate overall revealed the decreased trend gradually from south to north the law in the more than 0.25mm aggregation.4. Traditional destription, the CV of the soil aggregate corrosion resistance indicator belonged to the medium level, its rangevaried between 45.04%-75.0%. In spatial deffence, the dispersion rate mainly mainly focused in 19% or so, the content of soil organic mater (SOM) changed from 19 to 40g/kg, corrosion cndex was more than 35%, the range og dispersion coefficient was between 5% to 20%. The spatial maps of the soil corrosion resistance showed the character of northwest high and southeast low was found in dispersion rate, that of the dispersion coefficient was the increased trent from the center to around, and that of organic matter indicated overall the east high and the west low.5. The Peasron typical correlation analysis showed that percentage of aggregate destruction(PAD) correlated significantly with the aggregate degree, aggregation states, corrosion Index and SOM. The significant negative correlation was ovserved between dispersion rate and both aggregate degree and aggregation status. A distinct negative correlation was found between SOM and corrosion Index, the obvious correlation was not found among pH, dispersion coefficient and other indicators.