Apparent Change in Soil Depth and Soil Hardness in Forest Areas in Kampong Thom Province, Cambodia

Abstract

In the evergreen forests in Kampong Thom Province, Cambodia, soil depth and soil hardness apparently change from the rainy season to the dry season. In contrast, in deciduous and mixed forests, these parameters hardly change in either season. The apparent changes in soil depth and hardness would be strongly affected in the dry season by physical properties, including clay content and transpiration rates. At the DEFlog plot, hard soils were confirmed in the dry season from just below the surface to 4 m in depth. This fact suggests that the roots siphon off soil water from very deep under the surface of the ground. Assuming that the effective porosity of the soils was 0.09 m3 m−3, the soil water consumption rate in the dry season from just below the surface to 4.1 m in depth, occurring mainly by transpiration, was approximately 369 mm. In addition to this, a deeper soil layer above the groundwater level loses considerable soil water in the dry season.