Abstract: NEWCOP(Northeast Woods Competition Occupation Proccessor), a gap class model computer simulation model has been built to simulate the species composition dynamics of the northeast China forests, which simulates generation, growth and death of every tree on a forest stand. NEWCOP classifies the tree’s regeneration into 3 types: seedling, sprouting and diffuse so that the ecological theories such as seed bank, seedling bank and effect of environmental factors on regeneration can be applied to regeneration modeling. NEWCOP can deal with the incomplete shading deciduous trees on evergreen trees reasonably to simulate annual regeneration and growth of evergreen trees before the deciduous leave return during earlier summer. NEWCOP finds a new type of mortality: death induced by small relative diameter growth, which can simulate the death of bigger or old trees. The simulation validation along the environmental gradient shows :NEWCOP model can reproduce correct distribution of forest types, correct tree species composition of climax forests, correct succession pattern of main forest types in northeastern China forests, and correct DBH distribution of forest stand at some cases. The application simulation under climate change scenarios shows: Different climate change scenarios have different effects on the forests; The deciduous tree species may increase in tree species composition in the future; There may be a great decrease of the area in which forest can grow in the future ,and most decreases may occur within the first 100 years after simulation beginning.

Key words: Gap model, Northeastern China forests, Climatic change, Forest succession, Tree growth