Book excerpt: An understanding of the characteristics and the ecology of soils, particularly those of forest ecosystems in the humid tropics, is central to the development of sustainable forest management systems. The present book examines the contribution that forest soil science and forest ecology can make to sustainable land use in the humid tropics. Four main issues are addressed: characteristics and classification of forest soils, chemical and hydrological changes after forest utilization, soil fertility management in forest plantations and agroforestry systems as well as ecosystem studies from the dipterocarp forest region of Southeast Asia. Additionally, case studies include work from Guyana, Costa Rica, the Philippines, Malaysia, Australia and Nigeria.