BE/CBC: Coupling of Carbon and Water Cycles in a Cold, Dry Ecosystem: Integrative Physical, Chemical and Biological Processes and their Controls on CO2 Exchange

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Welker0221606This research effort will quantify the coupling of the carbon and water cycles and the interacting physical, chemical and biological (PCB) processes that control C exchange between cold, dry terrestrial ecosystems and the atmosphere. They are focusing on cold, dry ecosystems because: (1) understanding of carbon and water interrelationships and net C exchange is only rudimentary for this extreme environment, making it impossible to predict the vulnerability of this ecosystem to the expected anthropogenically-exacerbated warming; (2) these tundra systems are sufficiently simple allowing the quantification of all key components and the development of a system behavior conceptual model and (3) the vital role of unfrozen water in this cold, dry environment underlies the importance of thresholds and highly nonlinear interactions between PCB processes. Results will contribute to the understanding and the quantification of global carbon and water cycling, as well as to the understanding of extreme habitats on Earth, and possibly on other cold, dry planetary bodies.They will quantify the seasonal changes in the coupling of C and water at the leaf and ecosystem scales using in situ isotopic approaches, evaluate and quantify how the seasonal patterns of physical, chemical and biological processes interact to regulate the dynamics of net C exchange, and use a biogeochemical model to investigate net CO2 exchange and the complex PCB interactions under current climates and a range of likely future climate change scenarios and integrate these with arctic and global carbon budget estimates. The program will be based on articulating the complexities of carbon and water coupling under current conditions, but also on the responses of the biological, chemical and physical processes and interactions in response to field manipulations of winter and summer precipitation and warming. They anticipate that the study will result in a new insight into the adaptations of plant and microbial life in cold, dry ecosystems and the coupled nature of carbon and water in an ecosystem that is very different from more temperate ecosystems where most current understanding of these processes has originated. Furthermore, they expect to gain a more precise understanding of the extent to which this ecosystem responds to future climate change and the consequences of these changes for arctic and global C budgets.