Intellectual Merit: Recent observations attest to the profound ecological and societal consequences of climatic change in northern high latitudes, including a doubling of area burned in the boreal forests of western North America in the past 30 years, attributed primarily to anthropogenic warming. Fire responses to climatic transients are not straightforward. A major unknown in predicting arctic-system behavior is how climatic change may alter boreal fire regimes, which has potential to overshadow the direct effects of anthropogenic warming on vegetational patterns, energy flux, and biogeochemical cycling. Boreal forests occupy ~80% of the Arctic Ocean watershed and the proportion is expanding as treelines advance in response to climatic warming. Increased occurrence of boreal-forest fires may have pervasive effects on hydrological, biophysical, and biogeochemical processes that exert key controls on the tightly coupled climate system of arctic and boreal regions. In addition, fire-regime shifts and associated vegetational changes will have profound consequences to the animals and northern cultures that make use of both arctic and boreal landscapes. This project confronts our poor understanding of fire responses to climatic change in arcto-boreal Alaska by integrating paleorecords and computer modeling. The centerpiece of the project is its innovative and rigorous approach to understand patterns and mechanisms of climate-firevegetation interactions from the recent geological past through the near future. Charcoal processes of contemporary and recent burns will be monitored to parameterize a new numerical model of charcoal-fire relationships (CharSiM), a tool that greatly enhances the rigor of fire-history reconstruction. The results will be applied to interpret fire histories of the past 6000 years (focusing on the neoglacial transition and oscillations within the Little Ice Age) from sediment-charcoal records. Sediment-charcoal data will be collected with statistical criteria in two study areas that are characterized by contrasting fire regimes and recent climate anomalies. The fire records will be compared with climatic and vegetational reconstructions using state-of-the-art paleoecological and geochemical techniques. An iterative paleodata-modeling approach will be applied to elucidate mechanistic processes of climate-vegetation-fire interactions (e.g., lead-lag relationship, fuel dynamics) using ALFRESCO, a model developed and well tested for studying Alaskan boreal ecosystems. Finally, the improved ALFRESCO will be used to simulate regional fire regimes for the next 100 years based on a suite of forecast climate scenarios. Each of the research elements represents the forefront of current research in the respective areas, and together they promise to substantially advance the understanding of fire-climate-vegetation relations for the past, present, and future. Broad Impacts: This project should bring new insights into the variability of boreal fire responses to climatic change and to improve the robustness of a key model for predicting future changes in boreal ecosystems. The prognostic simulations of the 21st century fire regimes will be directly relevant to fire management planning and policy. An outstanding minority doctoral student has been an integral part of the team during the pilot study. Students will receive interdisciplinary training and interact with a broad research community to gain an integrative perspective of global change study. In addition, the researchers will engage local residents in fieldwork and give informal lectures to local scientists and communities. The research is enthusiastically endorsed by the leaders of federal fire management units in Alaska who will be involved in the execution of this project and the dissemination of research products. Educational materials will be produced for outreach to the general public and for dissemination through visitor interpretive activities of the Alaska Fire Service, the US Fish and Wildlife Service, and the National Park Service.
