Soil wettability in forested catchments in South Africa; as measured by different methods and as affected by vegetation cover and soil characteristics

Earlier studies in South Africa had shown that water repellency in the soils of timber plantations was associated with a greater risk of overland flow and soil erosion on mountain slopes. This paper reports on a follow-up study to determine how prevalent water repellent soils are in the forestry areas of South Africa, and to what extent this phenomenon is associated with specific vegetation types. Soils from a representative series of forestry sites around South Africa were sampled from beneath each genus or plantation type and the range of local vegetation types. These soils were dried at low oven temperatures and then subjected to a series of tests of soil wettability, namely, water drop penetration time, infiltration rate, critical surface tension and apparent advancing contact angle as determined by the equilibrium capillary rise test.