Forest ecology, silviculture, and forest yield study have always been and still are three basic fields of forest research. In the history of forestry research, it was forest yield study that started to develop seeking an answer to the question which method can be used for the assessment of the volume of forests and for getting the highest yield. At the beginning of the 60s, yield tables of mixed stands for all the domestic stand forming tree species were created, and later on also the related forest growth models were worked out. This work was assisted with long-term research programs (Rezső Solymos). There has always been a close relation between the examination of tree growth and studying site conditions. Soil investigation and climate conditions analysis came to be focused on especially at forest planting. The first complex site analyses are related to the forest planting of poplars on flood plains, oaks on saline soils, pine trees on bare lands, and tree planting on sandy areas between the Danube - Tisza Interfluve. The importance of this research increased until 1954, when the Department of Ecology came to be indepent from the department specialized on silviculture and forest planting. The first complex investigations of forest landscape were managed by Imre Babos in which, based on the forest typology system, policies of forest regeneration and forestation of Hungary were worked out. Site typology system was a new milestone in the further development of this work based on forest communities (Zoltán Járó). Ecophysiological studies with ecosystem approach were added to further research. Process examinations of the production of organic nutrient and water balance covered the most important natural and man-made forests. Fifty years later, in 2005, the two Departments were re-unified that reflects the close relation between the two fields and their increasing interdependence.