Soil hydrological properties and sediment transport in two headwater catchments with different vegetative cover at the Coastal Mountain Range in southern Chile

Abstract

Soil hydrological properties and sediment transport in two headwater catchments with native evergreen forest and plantation of Eucalyptus globulus, located at the Coastal Mountain Range in southern Chile, were studied. Streamflow loggers and sediment collectors were installed, infiltration rates were measured and soil hydrological properties, such as saturated hydraulic conductivity, porous continuity index and hydrophobicity were determined. The results showed significant differences in the infiltration rates between native forest and E. globulus plantation, since in the native forest they fluctuated between 703.3 ± 380.0 and 76.9 ± 56.7 mm h^-1, in March and July respectively, meanwhile in the plantation they fluctuated between 23.0 ± 19.7 and 6.7 ± 5.0 mm h^-1 in August and April, respectively (mean ± 1 SD). Saturated hydraulic conductivity under the native forest was signifcantly higher (P < 0.05) than it was in E. globulus plantation, indicating a greater water conductivity capacity in the soil under native forest. The porous continuity index was significantliy higher (P < 0.05) under native forest compared with E. globulus plantation. The suspended sediment concentrations showed great variations during the year, correlated with rainfall and streamflow fluctuations in both catchments. The annual suspended sediments rates were 305 and 368 kg ha^-1 year^-1 in the native and plantation catchments, respectively. The historical land use, especially in the E. globulus plantation, that at present still reflects a transition between prairie and plantation, explains the differences in the soil hydrological properties concerning native forest.