Soil erosion and overland flow from Acacia plantation forest in headwater catchment of Vietnam

To assess soil losses and overland flow in Acacia plantations of different ages, five plots (10m²/plot) was set up at different vegetation cover conditions (bare land, 4-month-old Acacia trees, 1-year-old Acacia trees, 2-year-old Acacia trees and 4-year-old Acacia trees) in Truong Son headwater, Hoa Binh, Vietnam. Soil erosion and overland flow was monitored over 75 storm events from September 2017 to October 2018. The main findings included: (1) Overland flow coefficient was highest at bare land (13.3 %), followed by 4month-old acacia (3.0 %), lower in Acacia forest at age 1 (1.5 %) and age 2 (1.4 %) and the lowest at 4-year-old Acacia (0.6 %); (2) The highest amount of soil loss was found in bare land (114.35 ton/ha/year) and decreased over ages of Acacia such as 30.33 ton/ha/year at 4- month-old Acacia, 13.90 ton/ha/year at 1-year-old Acacia, 13.22 ton/ha/year at 2-year-old Acacia and 3.94 ton/ha/6 month at 4-year-old Acacia; (3) Soil erosion and overland flow tended to be decreased due to increasing of Acacia ages with statistic significant difference (p-value < 0.01); (4) Soil erosion and overland flow in this study was higher than once of other previous studies. This suggests that more concern and applying suitable management for reducing the negative impact of Acacia plantation forest in headwater of Vietnam is necessary.