In 1992, a Forest Dynamics plot was initiated by the Royal Thai Forest Department in collaboration with Kasetsart and Mahidol Universities and CTFS/Harvard University at the Huai Kha Khaeng Wildlife Sanctuary, a World Heritage Site in western Thailand. The plot crosses a steep soil moisture gradient, forming a transect between dry evergreen dipterocarp and deciduous forest. Evergreen dipterocarp forest is a critically endangered habitat in the region, and often becomes converted into deciduous forest through degradation and fire. The area's abundant large game, including elephants and tigers, depends on each forest type in different ways and during different seasons. Understanding the dynamic relationship between these evergreen and deciduous forests will be fundamental to the conservation of both the forests and their wildlife.