How does planting trees and bushes on a steep hill affect topsoil on the hill

Muriel is an 86-year-old woman who tries to function independently but has suffered for several years with forgetfulness, especially with recent memories. she has trouble recalling the names of her best friends when they call on the phone, and she worries that she may have a form of dementia called alzheimer's disease huntington's disease schizophrenia parkinson's disease