Location: Watershed Physical Processes ResearchTitle: Root reinforcement to soils provided by common Ethiopian highland plants for gully erosion control Author
Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2018
Publication Date: N/A
Citation: N/A Interpretive Summary: Vegetation has shown to reduce gully erosion by stabilizing gully banks and heads. However, the effectiveness of such biological conservation measures has not been investigated for the sub humid Ethiopian Highlands. Scientists at the USDA, ARS, National Sedimentation Laboratory in collaboration with researchers at Cornell University and Bahir Dar University, Ethiopia, have investigated the root reinforcement of 26 indigenous and exotic plants found in the Debre Mawi watershed, northern Ethiopia. For a given plant species, the root biomass concentration had a greater effect on root reinforcement than root tensile strength. Plant species with a fibrous root system provided greater root reinforcement and could enhance gully bank stability for shallow gullies more than plants having a tap root system. The findings could contribute to the success of the nation-wide Ethiopian soil and water conservation campaign by providing science-based information on effectiveness of different plant species in controlling gully erosion.
Technical Abstract: Grasses and trees are often used to stabilize gully banks. However, the effectiveness of such biological conservation measures has not been investigated for the Ethiopian Highlands. This study, therefore, investigates the reinforcement that plant roots may provide to strengthen gully banks in Ethiopia. The root systems of 26 indigenous and exotic plant species of three plant types (grasses, shrubs, and trees) were sampled, and root tensile strength and distribution were determined. The RipRoot model was used to quantify the added shear strength derived from the plant roots. Among all tested roots, E. floccifolia (grass), Tephrosia (tree) and R. abyssinica (shrub) had the strongest roots. The root volumetric ratio in the top 0.6 m of soil ranged from 0.03 to 0.46%. D. abyssinica provided the maximum added shear strength (10.6 kPa) over this depth. For a given plant species, the root volumetric ratio had a greater effect on root cohesion than root tensile strength. Plant species with a fibrous root system provided greater cohesion values and could enhance gully bank stability for shallow gullies more than plants having a tap root system. Consequently, grasses have advantages over shrub and trees in stabilizing gully banks due to their fibrous root system.