B44B-01
The Stability of Peatland Carbon Stores to Global Change: Evidence for Enhanced Methane and Carbon Dioxide Production 

Thursday, 17 December 2015: 16:00
2010 (Moscone West)
Jeffrey Chanton1, Rachel Wilson2, Malak M Tfaily2, Stephen D Sebestyen3, Cassandra Medvedeff4, Karis J McFarlane5, Randy K Kolka6, Joel E Kostka7, Jason Keller4, Paul J Hanson8, Tom Guilderson5, Florentino de La Cruz9, William T Cooper10, Scott D Bridgham11 and Morton Barlaz9, (1)Florida State Univ, Tallahassee, FL, United States, (2)Florida State University, Tallahassee, FL, United States, (3)USDA Forest Service, Grand Rapids, MN, United States, (4)Chapman University, Orange, CA, United States, (5)Lawrence Livermore National Laboratory, Livermore, CA, United States, (6)U.S. Forest Service, Grand rapids, MN, United States, (7)Georgia Institute of Technology Main Campus, Atlanta, GA, United States, (8)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (9)North Carolina State University, Raleigh, NC, United States, (10)Florida State University, Department of Chemistry & Biochemistry, Tallahassee, FL, United States, (11)University of Oregon, Eugene, OR, United States
Abstract:

Peatlands sequester large stores of carbon in sedimentary sequences that can be meters thick. Peatlands can be separated into two main layers: the acrotelm, which is exposed to the atmosphere and dominated by living plants, and the catotelm, which tends to be anoxic and is where the majority of organic matter is stored. In response to warming climate, to what extent will peatland organic matter be activated to form additional CH4 and CO2 relative to current production rates? To predict the answer to this question the SPRUCE (Spruce and Peatland Responses Under Climatic and Environmental Change) project is being conducted in a bog ecosystem in northern Minnesota. The study is designed to improve predictive skill in peat and wetland-methane models by defining quantitative relationships among decomposition indices, microbial communities, and CO2 and CH4 production rates. The manipulation is being conducted in a staged approach, and deep warming through the entire ~2 m peat profile was initiated in June of 2014 at +0, +2.2, +4.5, +6.8 and +9C. Starting in summer 2015, the project will enhance both above and belowground temperature and CO2 levels. Following months of temperature enhancement there is no evidence of an effect on catotelm peat. In bog pre-treatment, control and treatment plots, microbial respiration and CO2 and CH4 production in the deep peat is driven primarily by recent plant production and to date, this trend continues in the catolem following treatment. Methane d13C and fractionation factors are invariant across the treatments, as are gas concentrations at depth. Surface CH4 emission, however, has shown a positive correlation with peat temperature, and measurements of CH4 production in incubations across the depth profile suggest that surface peat is more responsive to increases in soil temperature, apparently driving the emission response. Shifts in the composition and metabolic potential of microbial communities are being examined using next generation sequencing, metagenomic, and metatranscriptomic approaches. Prior to heating, microbial communities showed strong vertical stratification correlated to peat decomposition and humification, while little spatial or temporal variation was observed. Peat samples from after 1 year of heating are now being processed and data will soon be available.


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