A review of modern approaches existing nowadays in ecological modelling of forest ecosystems in boreal and temperate forests. The book contains data on contemporary approaches in intensively developed simulation modelling of forest stands, soils and whole ecosystems as well; an analysis of existing spatial forest models and their significance and development; and a comprehensive discussion of theoretical (analytical) models of forest communities. The idea of a system of forest models for more effective solving of different theoretical and practical problems is also discussed. This work is particularly useful in its critical reviewing of modern achievements in forest ecosystem modelling and its discussion of more promising trends of forest modelling with an increase of their practical significance in the near future.