Eight Mile Lake Research Watershed, Thaw Gradient: Seasonal thaw depth 2004-2018

In this larger study, we are asking the question: Is old carbon that comprises the bulk of the soil organic matter pool released in response to thawing of permafrost? We are answering this question by using a combination of field and laboratory experiments to measure net carbon exchange, radiocarbon isotope ratios in soil organic matter, soil respiration, and dissolved organic carbon, in tundra ecosystems. The objective of these proposed measurements is to develop a mechanistic understanding of the SOM sources contributing to C losses following permafrost thawing. We are making these measurements at an established tundra field site near Healy, Alaska in the foothills of the Alaska Range. Field measurements center on a natural experiment where permafrost has been observed to warm and thaw over the past several decades. This area represents a gradient of sites, each with a different degree of change due to permafrost thawing. In this area, we eatablished three sites with different degrees of disturbance from the permafrost thaw: 1) a relatively undisturbed tussock tundra (Minimal Thaw site), 2) a site adjacent to to the borehole which is monitoring permafrost thaw since 1985 with intermediate degree of disturbance (Moderate thaw site) and 3) a site where permafrost thaw apeared to have started more than three decades ago (Extensive thaw site) As such, this area is unique for addressing questions at the time and spatial scales relevant for change in arctic ecosystems.