Project Funding: 2014 - 2017

NRA: 2013 NASA: Carbon Cycle Science   

Funded by USDA

Abstract:
Global soil carbon stocks are 2-4 times greater than atmospheric CO2-C. Soils and wetlands are significant sources and sinks for atmospheric CO2, CH4 and N2O. Soil greenhouse gas (GHG) emissions are likely to play a significant role as biotic feedbacks to climate change. However, these complex processes, involving carbon, nitrogen, and oxygen substrates and inhibitors, interactions with plant processes, and environmental influences of temperature, moisture, and gas transport, remain challenging to simulate in earth system models. Here we propose a novel integration of measurement and modeling of these three GHGs in upland and wetland soils at the Howland Forest AmeriFlux site. Our main objective is to improve understanding of and modeling capacity for interactions of belowground temperature, moisture, and substrate supply as controllers of net soil emissions of CO2, CH4, and N2O. The proposed work is central to Theme 3, as we seek to refine the understanding of critical belowground soil processes, but is also relevant to Theme 1 due to the boreal-temperate transition forest locale, Theme 2 because of the upland-wetland transitions, and Theme 6 due to applicability of modeling to Ameriflux and NACP networks. Because the processes of CO2, CH4, and N2O production and consumption are inter-linked through some common substrates and the contrasting effects of O2 as either an essential substrate or a potential inhibitor, the mechanistic simulation of fluxes of any one gas must be consistent with mechanistic simulations and observations of fluxes of the other gases. Simulating the fluxes of one gas alone would be a simpler task, but simulating all three gases simultaneously and linking to aboveground processes of carbon supply provides multiple constraints and affords greater confidence that the most important mechanisms are aptly simulated. We take advantage of a data-rich study site, including ongoing NASA and DOE funded measurements of soil profiles, chamber fluxes, eddy covariance fluxes, forest inventory and biomass growth, leaf area, litterfall, and other ecosystem data at Howland, to build and test an integrated modeling framework, adding functions and complexity of model structure as warranted by the data-model fusion. Global soil carbon stocks are 2-4 times greater than atmospheric CO2-C. Soils and wetlands are significant sources and sinks for atmospheric CO2, CH4 and N2O. Soil greenhouse gas (GHG) emissions are likely to play a significant role as biotic feedbacks to climate change. However, these complex processes, involving carbon, nitrogen, and oxygen substrates and inhibitors, interactions with plant processes, and environmental influences of temperature, moisture, and gas transport, remain challenging to simulate in earth system models. Here we propose a novel integration of measurement and modeling of these three GHGs in upland and wetland soils at the Howland Forest AmeriFlux site. Our main objective is to improve understanding of and modeling capacity for interactions of belowground temperature, moisture, and substrate supply as controllers of net soil emissions of CO2, CH4, and N2O. The proposed work is central to Theme 3, as we seek to refine the understanding of critical belowground soil processes, but is also relevant to Theme 1 due to the boreal-temperate transition forest locale, Theme 2 because of the upland-wetland transitions, and Theme 6 due to applicability of modeling to Ameriflux and NACP networks. Because the processes of CO2, CH4, and N2O production and consumption are inter-linked through some common substrates and the contrasting effects of O2 as either an essential substrate or a potential inhibitor, the mechanistic simulation of fluxes of any one gas must be consistent with mechanistic simulations and observations of fluxes of the other gases. Simulating the fluxes of one gas alone would be a simpler task, but simulating all three gases simultaneously and linking to aboveground processes of carbon supply provides multiple constraints and affords greater confidence that the most important mechanisms are aptly simulated. We take advantage of a data-rich study site, including ongoing NASA and DOE funded measurements of soil profiles, chamber fluxes, eddy covariance fluxes, forest inventory and biomass growth, leaf area, litterfall, and other ecosystem data at Howland, to build and test an integrated modeling framework, adding functions and complexity of model structure as warranted by the data-model fusion.