Modeling the current and future ranges of Turkish pine (Pinus Brutia) and oriental beech (Fagus Orientalis) in Turkey in the face of climate change

Yalçın, Semra
Climate change is widely recognized to have potential impacts on global biotic and abiotic systems. One of the major impacts is expected on species distributions. Species distribution models (SDMs) are used for estimating the relationship between species occurrences at sites and environmental and/or spatial characteristics of those sites. SDMs can be used to understand possible responses of species to climate change. Despite some sources of uncertainty, projections onto future climate are useful and cost-effective tools for managers, especially given the increasing urgency to inform management authorities under the pressure of climate change. This thesis aims to model current and potential future distributions of two economically and ecologically important tree species, Turkish pine and oriental beech, in the face of climate change, and to assess the effect of using different data sets and modeling methods in model setups on SDM accuracy. The BIOMOD 2 framework, implemented in the open source software R (version 2.15.1) was used to build the distribution models. In model calibrations, different data sets of response variables were used with eight different modeling methods. Moreover, ensemble forecasting was carried out by using a proportional weighted average of each model's predictions (trained models) based on the AUC scores. Performances of the current predictions were compared to 1/25.000 scale forest stand maps and evaluated using various metrics. Future distributions for each species were projected according to IPCC SRES emission scenarios A2 and B2 of the HadCM3 global circulation model. Based on the results of the ensemble models, climatically suitable areas of Turkish pine trees were predicted to shift to higher altitudes and toward the north and northeastern regions of Turkey. Potentially suitable areas for oriental beech were expected mainly to be lost and its overall distribution was predicted to be narrower in the future. While Turkish pine was likely to gain large climatically suitable areas by 2080, expansion into suitable areas by oriental beech in the future was predicted to be very limited. An important proportion of habitats where Turkish pine and oriental beech currently occur were predicted to become unsuitable in the future. Overall, climate change is expected to have significant impacts on the distributions of Turkish pine and oriental beech forests in Turkey. Depending on whether fast dispersal to newly occurred suitable habitats will be possible or not, it can be stated that serious ecological, economic and social consequences will probably come out.