对石林地区洼地边坡和底部红壤的物理、化学性质差异进行了研究 ,结果表明土壤的化学成分、水分含量和粒度组成都和所处的地貌部位有关。洼地底部的土壤细粘粒含量、水分含量、Al2 O3和Fe2 O3含量低于洼地边坡 ,而粗粉粒含量、SiO2 含量则高于洼地边坡。土壤SiO2 含量随粒径变细而减少 ,Al2 O3和Fe2 O3则随粒径变细而增加 ,土壤中水分含量与细粘粒含量正相关 ,与粗粉粒含量负相关。因此 ,不同地貌部位土壤的粒度组成差异决定了洼地底部和边坡的水分含量及化学组成的差异

Limestone dolines are much developed in Lunan Stone Forest National Park with soil mantle We choose 9 sites in the bottom or slope of 4 dolines in Lunan Stone Forest in order to study the soil particle size distribution, water content(%), chemical composition of soil developed in the doline bottom or on the slope and their relationship with doline development Study shows that soil water content, chemical composition and particle size distribution are all controlled by karst topography The soil in the bottom of the depression has a lower water content, total Al 2 O 3 and Fe 2 O 3 content than that of the soil in the slope of the depression, However, total SiO 2 of soil in the doline bottom is higher than that of the slope We mainly study the clay and silt content of the soil mantle soil in doline bottom has higher silt content and less clay content than that of the soil on the slope Research results show that with the increase of soil fine grain size, the SiO 2 content decreases while both of Al 2 O 3 and Fe 2 O 3 content increase The water content of soil is highly positive related with content of fine grain size and strongly negative related with content of coarse silt content In order to determine the limestone erosion rate at different depths, 27 limestone tablets were buried at different depths(20 to 60 or 120 cm, one layer every 20 cm) of soil, which were developed in the bottom and slope of a doline in November 1999 Two years later(November, 2001), 25 tablets were exhumed and sent to lab to measure their weight loss then calculate dissolution rate Result of dissolution experiment shows that limestone dissolution rate in the soil of doline bottom is much higher than that in soil on the slope At the same time, result of correlation analysis shows that limestone dissolution rate is highly positive related with content of coarse silt content(R 2 =0 85) and strongly negative related with content of fine grain size(R 2 =0 84) To some extent, even though limestone dissolution rate was decided by soil CO 2 concentration and soil chemical composition, it is still affected by the soil particle size distribution