Persistent net release of carbon dioxide and methane from an Alaskan lowland boreal peatland complex

• Published in: Global Change Biology
• Main Authors: Euskirchen, Eugénie S., Edgar, Colin W., Kane, Evan S., Waldrop, Mark P., Neumann, Rebecca B., Manies, Kristen L., Douglas, Thomas A., Dieleman, Catherine, Jones, Miriam C., Turetsky, Merritt R.
• Other Authors: National Science Foundation, Northern Research Station
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: Peat; Peat plateau; permafrost; Thermokarst; Alaska
• Online Access: http://dx.doi.org/10.1111/gcb.17139; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.17139

Abstract Permafrost degradation in peatlands is altering vegetation and soil properties and impacting net carbon storage. We studied four adjacent sites in Alaska with varied permafrost regimes, including a black spruce forest on a peat plateau with permafrost, two collapse scar bogs of different ages formed following thermokarst, and a rich fen without permafrost. Measurements included year‐round eddy covariance estimates of net carbon dioxide (CO 2 ), mid‐April to October methane (CH 4 ) emissions, and environmental variables. From 2011 to 2022, annual rainfall was above the historical average, snow water equivalent increased, and snow‐season duration shortened due to later snow return. Seasonally thawed active layer depths also increased. During this period, all ecosystems acted as slight annual sources of CO 2 (13–59 g C m −2 year −1 ) and stronger sources of CH 4 (11–14 g CH 4 m −2 from ~April to October). The interannual variability of net ecosystem exchange was high, approximately ±100 g C m −2 year −1 , or twice what has been previously reported across other boreal sites. Net CO 2 release was positively related to increased summer rainfall and winter snow water equivalent and later snow return. Controls over CH 4 emissions were related to increased soil moisture and inundation status. The dominant emitter of carbon was the rich fen, which, in addition to being a source of CO 2 , was also the largest CH 4 emitter. These results suggest that the future carbon‐source strength of boreal lowlands in Interior Alaska may be determined by the area occupied by minerotrophic fens, which are expected to become more abundant as permafrost thaw increases hydrologic connectivity. Since our measurements occur within close proximity of each other (≤1 km 2 ), this study also has implications for the spatial scale and data used in benchmarking carbon cycle models and emphasizes the necessity of long‐term measurements to identify carbon cycle process changes in a warming climate.