Root Strategies for Rill and Gully Erosion Control

Abstract

Many studies attribute the effects of vegetation in reducing water erosion rates to the effects of the above-ground biomass. The effects of the below-ground biomass on flow erosivity and topsoil resistance to concentrated flow erosion are much less studied. However, roots play an important role in controlling soil erosion rates, especially when the above-ground biomass disappears (e.g. due to fire, drought, harvest, grazing) and particularly when incisive processes are concerned. Roots affect properties of the soil, such as soil roughness, infiltration rate, aggregate stability, moisture content, soil cohesion and organic matter content, all of which control soil erodibility to various degrees. It is generally recognised that plant roots contribute to the overall cohesion of the soil. Moreover, roots were also assumed to have a flow-retarding effect. The main objective of this chapter is therefore to discuss the mechanical and hydraulic effects of plant roots during concentrated flow erosion which allows us to better understand and predict soil erosion rates during concentrated flow erosion. Several empirically based relationships that can be used to predict the erosion-reducing effects of plant root during concentrated flow erosion are presented. The relative contribution of roots versus shoots in preventing soil detachment will also be addressed. Finally, a methodology to evaluate plant traits (both shoots and roots) for gully erosion control is proposed.