Distribution of the West Himalayan forest types dominated by Pinus roxburghii, P. wallichiana, and Quercus semecarpifolia is discussed within the pattern of forest distribution in the eastern, humid part of the Nepal Himalaya. All of the principal zonal forests of the western Himalaya are found in the wet eastern Himalaya, where they occur as relict patches on local dry habitats, such as south-facing convex slopes. The successional status of these western Himalayan species changes along the west-to-east gradient of the Himalaya: in the western Himalaya they persist as climax species; from the central to the eastern Himalaya they are pioneer trees in disturbed sites; and in the wet eastern Himalaya they comprise relict patches. The pioneer trees found in the eastern Himalaya are classified into four ecological types according to their nature: the habit pioneer, the habitat pioneer, the undifferentiated canopy component, and the understory component. The three western Himalayan elements discussed in this study are included in the habitat pioneer type. Species corresponding to each of the four pioneer types can be found throughout wet Southeast Asia, including Japan and tropical Asia.