The Manchurian mixed forests ecoregion (WWF ID:PA0426) covers the forested hills surrounding the river plains of northern China, Russia, North Korea, and South Korea. The ecoregion supports a number of rare species due to the relative isolation, the diversity of habitat, with mixed forests of deciduous Mongolian oak and conifers of Korean pine. Because mountains rise above the region on three sides, with plains and wetlands below, the area supports high biodiversity as a transition zone.