Modeling Effects Of Climatic Changes On Coniferobroadleaved Forest And Secondary Deciduous Broadleaved Forest In Northeast China

To study effects of global climatic changes (GCC) on structure and functions of coniferobroadleaved mixed forest and secondary deciduous broadleaved forest in northeast China, a new model FPBG was established, which used a from-bottom-to-up method to simulate the tree growth form annual photosynthesis rate without using LAI and then model the dynamics of the forests by gap model. The model was validated for all its major components, which indicates that the model is suitable to simulate the dynamics of forest at different climate scenarios. The DBHs of all the trees in 997 plots of the national forest inventory in 1995 were input in the model together with the simulated daily weather data at the normal and Hadley scenarios to study the responses of the forests to climatic changes. The results show that climatic changes will reduce stand density in the study area since the 67th year from now. GCC will increase the stand biomass at the first 160 years of simulation, then decrease it between the 161st to 400th year and then increase it a bit for the rest 100 years, which indicates that GCC can increase stand biomass at their early restoration stage and almost have no effect at the steady stage. GCC can alter stand composition. It will decrease the stem number and biomass of coniferous species, increase that of broadleaved species in the early stage of the restoration of the current forests (the first 200 years of study time for stem number and 100 years for biomass) and do contrarily at the later stage (the rest study time). It will change the dominant species evaluated either by stem number or by biomass. The responses of the 12 species in the study region to GCC vary. Climatic changes cause species like Korean pine, Scotch pine, spruce, fir, Mongolian oak, Armur linden, David poplar, Asian white birch and mono maple increasing their stem number percentages in stand and species like Manchurian walnut, Manchurian ash, Larch and cork tree reducing their stem number percentages in stand. It also cause species like Korean pine, Scotch pine, Manchurian walnut and Manchurian ash, spruce and fir, Mongolian oak increasing their biomass percentages in stand, though at first 100 year a bit decrease, and species like larch, David poplar, Asian white birch, mono maple reducing their biomass percentages in stand. The biomass percentages of cork tree and Armur linden increase at some period of the simulation and decrease at some other time when climate changes. The above results also indicate that GCC can helpthe recovery of the formerly dominant species such as Korean pine, fasten the transition from early stage (pioneer species dominated) to latter stage by significantly reducing the biomass percentages of pioneer species in stand.