Changes in microstructure of surface soil through a slope

Abstract

Qualitative description by micromorphological observation was compared with quantitative soil physical and micromorphological measurements. Morphological changes of the soil structure appears to be related to the pore type composition and pore size distribution. Moreover, the pore size distribution determined by image analysis was found to be compatible with the results obtained by indirect measurement of the soil moisture characteristic curve. From 20 thin sections of soil surface on a slope, the high variability of the soil structure observed was reflected on the pore composition. The difference in the moisture conditions on the slope may have influenced the soil structure. In the upper slope with higher disturbance than in the middle and bottom slopes, the soil showed mainly a platy structure that was formed by detachment and rearrangement of soil materials. In the middle slope and bottom slope, a vesicular structure was commonly observed as a result of repeated wetting and drying processes. Pore type composition could reflect the soil conditions under which the soil structure was formed. On the other hand, the proportion of pores with a diameter between 75–300 μm increased from the upper slope to the bottom slope. Pore size distribution may reflect the changes of the soil structure through a slope.

Key Words:

• micromorphology
• pore size distribution
• pore type
• soil structure change