2006 Volume 48 Issue 1 Pages 17-24
Forest soil has the capacity to retain rainwater through what is known as soil porosity. In order to compare the water-retaining capacity of forest soils under different vegetation types, the porosity and the maximum water holding capacity (MWHC) were measured at both unthinned plantations and adjacent natural forest stands, which had developed on the same slope in an upstream basin of the Yoshino River in the Shikoku district of western Japan. Soil samples were taken at 0 to 20 cm depths at each stand. The porosity of the natural forest stands were 6.4% higher than those of the unthinned plantations (p< 0.001). The MWHC was also higher in the natural forest stands, by 8.3% (p< 0.001). The porosity and the MWHC of unthinned plantations were lower than the natural forest stands that have thicker Ao and A horizons. The forest soils with much humus have bigger water-retaining capacity, which may increase by thinning of plantations if the thickness of A horizon increases.
