干旱区生态环境知识资源中心

9 topsoil under 3 karst vegetations (Forest, shrub and herb) developed from limestone in Guiyang, Guizhou, P. R. China were collected to analysis the relationships between soil structure stability and soil erodible characteristics. Soil organic matter content in forest was higher than in shrub and herb, the content of water stable aggregate correlated best with the content of soil organic matter (r = 0.950**, n = 9).The mean composition of >0.25 mm water stable aggregate was 58.72% in forest soil, and was 142% and 257% times more than in shrub and herb, which showed that soil water stability in forest was stronger than in shrub and herb. Better plant covered can improve soil structure stability, and enhance the ability of soil resisting slaking and scouring. Correlation analysis showed that soil resisting slaking index and soil resisting scouring index was statistically significant correlated with > 0.25mm water stable aggregate, ratio of aggregate destruction, index of MWD (mean weight diameter) change, and soil aeration porosity, correlation coefficient were 0.989, 0.991, - 0.871, and 0.977, and 0.978, -0.987, -0.928, 0.984 respectively, which indicates that soil structure stability will change to be worse as vegetation evolution from forest to herb. In karst area, it is very important to protect natural forest, and increase plant covering so as to prevent karst rocky desertification.