| Summary: | The summer of 2015 was an extraordinary year for fire in the Arctic, including in the Yukon-Kuskokwim Delta, presaging a future where tundra and boreal fire is far more common. Remarkably, the area burned in the YK Delta in 2015 exceeds the total area burned from 1940-2014 combined. The response of the YK Delta in the first year post-fire will set the stage for longer-term changes in delta carbon storage and transport among tundra, aquatic and marine systems, and to the atmosphere. Quantifying carbon export and understanding the immediate ecosystem response to fire is critical because long-term recovery is, to a considerable degree, dependent on short-term responses. A major question that this research will address is how fire influences the amount and form of carbon transported from delta ecosystems seasonally and in the first year following fire. Ultimately, these results will inform long-term trajectories of the vulnerability and fate of delta carbon pools. This research will significantly improve our understanding of the role of fire in the loss of both modern and ancient carbon from arctic river deltas, which contain >10% of the Arctic's massive permafrost carbon store. Arctic river deltas are hotspots for carbon storage, occupying <1% of the pan-Arctic watershed but containing >10% of carbon stored in arctic permafrost. They are also heterogeneous mosaics of linked terrestrial and aquatic ecosystems, and are susceptible to changes in land, river, and marine systems. The vulnerability of carbon stored in arctic river deltas is a major unknown and is critically important as climate warming and increasing fire frequency may make this carbon vulnerable to transport to aquatic and marine systems and to the atmosphere. The goal of this proposal is to examine the immediate effects of fire on carbon storage in the Yukon-Kuskokwim Delta and exchange between terrestrial and aquatic components of the Delta. By extension this work will yield critical insights into how the carbon balance of deltas in the arctic system will change over the coming decades as warming continues and fire frequency increases. This dataset includes soils and permafrost collected during the summer 1 year after the fires. Soil and permafrost horizons are described, and measured for bulk density, soil moisture, volumetric ice content, pH, soil organic matter content, extractable nitrogen and carbon content, and cryo-structures are described,
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