Abstract

Vegetation controls erosion by dissipating the erosive forces of rainfall and runoff (erosivity—the strength of the forces causing erosion) and by reducing the susceptibility of soil to erosion (erodibility—how easily soil can be detached and transported). Vegetation alters the partitioning of rainfall between the amount that soaks into the soil, the amount retained on the wet vegetation, and the amount that runs off the land and may cause soil erosion. Vegetation reduces the erosive forces by absorbing raindrop kinetic energy, by reducing the runoff volume, and by slowing runoff velocity. Vegetation reduces soil erodibility by increasing the formation of erosion-resistant aggregates, binding aggregates together with roots, and increasing the soil’s capacity to absorb water. Vegetation may cover the entire soil surface, as with crops, cover crops, or forests, or it may be limited to specific critical areas, as with various types of conservation buffers. This entry reviews the mechanisms and processes by which vegetation reduces soil erosion by water, with emphasis on vegetative buffers. Crop residue effects are considered in another entry.