Richardson, Curtis (Neal): Duke University (Project Lead)
Project Funding:
2014 - 2017
NRA: 2013 NASA: Carbon Cycle Science
Funded by DOE
Abstract:
Earth System Models (ESMs) predict increased frequency of extreme wet and dry periods in the subtropics and tropics over the next century, resulting in uncertain carbon (C) budgets and greenhouse gases (GHG) fluxes. Globally, approximately 1/3 of peat stores are found in subtropical and tropical peatlands (STPs) formed from high-lignin woody biomass. STPs along the Atlantic coast from North Carolina (NC) to Florida (FL) to tropical Panama (PN) have persisted through climate and sea level changes over the last 4000 years and continue to accrete peat even under climate driven conditions of drought,
warmer temperatures and fire. Our questions are: 1) how do these stressed non-sphagnum peatlands accumulate and store C, and 2) can insights gained from studying their natural processes and control mechanisms provide management guidelines for vast STPs and boreal peatlands subject to increasing climate forcing. While most studies focus on northern peatlands, globally important STPs remain woefully underrepresented in ESMs. We propose a 3-year experimental comparison across STPs to reveal the key process-level mechanisms controlling soil C stabilization, accumulation, and long-term storage potential (Theme 3, topic 2). Our work will foster new strategies and predictive threshold models to facilitate recovery of disturbed STPs subjected to climate change, fire and lower water tables either by drainage or drought. Elucidation of control mechanisms will also yield perspective towards understanding the effects of global warming and drought on boreal Sphagnum peatlands undergoing climate-induced shifts to wooded plant communities. Our main hypothesis is that the STP native-fire-adapted shrubs/trees communities produce higher polyphenol litter than Sphagnum/Carex communities. This production difference, in conjunction with climate induced regimes of frequent low-intensity fire, creates recalcitrant decomposition-resistant peat by a dual “latch key mechanism” consisting of high phenol and black carbon (BC, complex aromatics). Together these retardants reduce GHG flux, and C decomposition of STPs peats under altered hydrologic conditions, higher temperatures and drought. Specific objectives include: I: Identify and compare process-level mechanisms controlling peat accretion and C losses from shrub-bogs in NC, subtropical Cladium/shrub peats in FL Everglades, to tropical Myrica-Cyrilla bogs in PN. This never-before-studied latitudinal gradient will allow experimental quantification of biotic (plants type) and abiotic (low-intensity fire and drought) contributions to resultant high phenol/low carbon quality litter and specific BC aromatics; II: Assess the composition and origin of aromatic compounds in peat and porewater at the molecular level and the importance of fire derived aromatic compounds limiting peat decomposition using multiple advanced analytical techniques including Pyrolysis GC-MS, GC-MS, LC-MS, NMR, FTIR, FT-ICR-MS and 3-Dimensional Excitation-Emission Matrix (EEM) fluorescence spectroscopy; III: Experimentally (field to microcosm scale) determine peat decomposition, GHG fluxes and DOC loss integrated with soil C chemistry, soil bacterial/fungal composition, enzyme activities, and hydrologic properties to enhance our understanding of controls on C storage and fluxes. The field study will leverage data and research site infrastructure at an ongoing drainage GHG study in NC, USFWS Pocosin Lakes and with ORNL and USFS investigators working at the MN SPRUCE site and with scientists at the Smithsonian Tropical Institute in PN. Our research spans themes 3.1.1,.2 and .3. Our project provides the first N to S comparative analysis of peatland C chemistry, tests a new dual control model for sustaining C, innovative analytical C chemistry data, and integrative data for modeling in support of NASA’s Earth Science Program goals to quantify changes in atmospheric CO2 and CH4 concentrations, and terrestrial and aquatic carbon storage.
Publications:
Wang, H., Richardson, C. J., Ho, M. 2015. Dual controls on carbon loss during drought in peatlands. Nature Climate Change. 5(6), 584-587. DOI: 10.1038/nclimate2643
Wang, H., Richardson, C. J., Ho, M., Flanagan, N. 2016. Drained coastal peatlands: A potential nitrogen source to marine ecosystems under prolonged drought and heavy storm events--A microcosm experiment. Science of The Total Environment. 566-567, 621-626. DOI: 10.1016/j.scitotenv.2016.04.211
Winton, R. S., Flanagan, N., Richardson, C. J. 2017. Neotropical peatland methane emissions along a vegetation and biogeochemical gradient. PLOS ONE. 12(10), e0187019. DOI: 10.1371/journal.pone.0187019
More details may be found in the following project profile(s):