Uncertainty in forest landscape response to global climatic change

Recently, many studies revealed that 1) the interactions between species may play an important role in community response to climatic change; 2) not only the direct effect of temperature, but also the precipitation, CO2 and the interaction between the climate variables may have important influences on species interaction and thus on community’s response to climatic change; and 3) the community responses may totally different under different climatic change scenarios. In this study, we coupled a forest landscape model LANDIS-II and a forest process model PnET-II to examine the variability/uncertainty in a transitional forest landscape (in the Boundary Water Canoe Area (BWCA)) response to climatic change. We also quantify the uncertainty contribution by different climate variables including temperature, precipitation, CO₂ and photosynthetic active radiation (PAR). The predicted response to climatic change results from the differential responses of 14 tree species under 209 possible climatic change scenarios, based on predicted climate data structure obtained from the IPCC Third and Fourth Assessment Report. The results show that, under the control scenario of continuing the historic 1984-1993 mean climate, the BWCA forest landscape will be a spruce-fir dominated boreal forest in 400 years. Under predicted climatic change, the BWCA forest will remain as spruce-fir dominated boreal forest in only ~44 percent of the 209 simulations, while the remaining will be pine dominated mixed forest. However, if there is an interaction between temperature and [CO2] enrichment which would results in 5 ^oC increase in optimum photosynthetic temperature, the BWCA forest will remain as spruce-fir dominated boreal forest in ~73 percent of the 209 simulations. As for the source of uncertainty, the most important source of uncertainty in forest landscape response to climatic change comes from the variability of temperature. The second most important is PAR, the third is CO₂ and the least important is precipitation.