This inter-disciplinary book provides the latest advanced knowledge of plant effects on vegetated soil properties such as water retention capability, water permeability function, shear strength, slope hydrology, movements and failure mechanisms, and applies this knowledge to the solution of slope stability problems. It is the first book to cover in detail not only the mechanical effects of root reinforcement but more importantly the hydrological effects of plant transpiration on soil suction, soil shear strength, and water permeability. The book also offers a fundamental understanding of soil-plant-water interaction. Analytical equations are provided for predicting the combined hydrological and mechanical effects of plant roots on slope stability. A novel method is also given for simulating transpiration-induced suction in a geotechnical centrifuge. Application of this method to the study of the failure mechanisms of vegetated slopes reinforced by roots with different architectures is discussed. This book is essential reading for senior undergraduate and postgraduate students as well as researchers in civil engineering, geo-environmental engineering, plant ecology, agricultural science, hydrology and water resources. It also provides advanced knowledge for civil engineers seeking "green" engineering solutions to combat the negative impact of climate change on the long-term engineering sustainability of infrastructure slopes. Professionals other than civil engineers, such as ecologists, agriculturists, botanists, environmentalists, and hydrologists, would also find the book relevant and useful.