Quantifying the effect size of changing environmental controls on carbon release from permafrost-affected soils

Christina Schaedel1, Martin Karl-Friedrich Bader2, Edward Schuur3, Rosvel G Bracho4, Petr Capek5, Sarah L De Baets6, Katka Diakova5, Jessica Gilman Ernakovich7, Iain P Hartley8, Colleen M. Iversen9, Evan S Kane10, Christian Knoblauch11, Massimo Lupascu12, Susan Natali1, Richard J Norby13, Jonathan A O'Donnell14, Taniya Roy Chowdhury13, Hana Santruckova5, Gaius R Shaver15, Victoria L Sloan16, Claire C Treat17 and Mark P Waldrop18, (1)Woodwell Climate Research Center, Falmouth, United States, (2)New Zealand Forest Research Institute, Rotorua, New Zealand, (3)Univ Florida, Gainesville, United States, (4)University of Florida, School of Forest Resources and Conservation, Ft Walton Beach, FL, United States, (5)University of South Bohemia, Ceske Budejovice, Czech Republic, (6)University of Exeter, Exeter, United Kingdom, (7)University of New Hampshire, Natural Resources and the Environment, Durham, United States, (8)University of Exeter, Department of Geography, Exeter, United Kingdom, (9)Oak Ridge National Laboratory, Climate Change Science Institute and Environmental Sciences Division, Oak Ridge, United States, (10)Michigan Technological University, College of Forest Resources and Environmental Sciences, Houghton, United States, (11)University of Hamburg, Institute of Soil Science, Hamburg, Germany, (12)Univ of California, Irvine, Irvine, CA, United States, (13)Oak Ridge National Lab, Oak Ridge, TN, United States, (14)National Park Service Anchorage, Anchorage, AK, United States, (15)Marine Bio Lab, Woods Hole, MA, United States, (16)ORNL, Bristol, United Kingdom, (17)University of Alaska Fairbanks, Fairbanks, AK, United States, (18)U.S. Geological Survey, Geology, Minerals, Energy, and Geophysics Science Center, Moffett Field, United States
Abstract:
High-latitude surface air temperatures are rising twice as fast as the global mean, causing permafrost to thaw and thereby exposing large quantities of previously frozen organic carbon (C) to microbial decomposition. Increasing temperatures in high latitude ecosystems not only increase C emissions from previously frozen C in permafrost but also indirectly affect the C cycle through changes in regional and local hydrology. Warmer temperatures increase thawing of ice-rich permafrost, causing land surface subsidence where soils become waterlogged, anoxic conditions prevail and C is released in form of anaerobic CO2 and CH4. Although substrate quality, physical protection, and nutrient availability affect C decomposition, increasing temperatures and changes in surface and sub-surface hydrology are likely the dominant factors affecting the rate and form of C release from permafrost; however, their effect size on C release is poorly quantified. We have compiled a database of 24 incubation studies with soils from active layer and permafrost from across the entire permafrost zone to quantify a) the effect size of increasing temperatures and b) the changes from aerobic to anaerobic environmental soil conditions on C release. Results from two different meta-analyses show that a 10°C increase in temperature increased C release by a factor of two in boreal forest, peatland and tundra ecosystems. Under aerobic incubation conditions, soils released on average three times more C than under anaerobic conditions with large variation among the different ecosystems. While peatlands showed similar amounts of C release under aerobic and anaerobic soil conditions, tundra and boreal forest ecosystems released up to 8 times more C under anoxic conditions. This pan-arctic synthesis shows that boreal forest and tundra soils will have a larger impact on climate change when newly thawed permafrost C decomposes in an aerobic environment compared to an anaerobic environment even when accounting for the higher heat trapping capacity of CH4 over a 100-year timescale.
Back to: Carbon in the Arctic: Influence of Climate Change in Aquatic and Terrestrial Ecosystems II