U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights

Predicting Long-Term Carbon Sequestration in Response to CO2 Enrichment
Published: April 27, 2015
Posted: November 25, 2015

Large uncertainty exists in model projections of the land carbon sink response to increasing atmospheric carbon dioxide (CO2). Free-Air CO2 Enrichment (FACE) experiments lasting a decade or more have investigated ecosystem responses to a step change in atmospheric CO2 concentration. To interpret FACE results in the context of gradual increases in atmospheric CO2 over decades to centuries, a recent study used a suite of seven models to simulate the Duke Forest and Oak Ridge FACE experiments extended for 300 years of CO2 enrichment. It also determined key modeling assumptions that drive divergent projections of terrestrial carbon uptake and evaluated whether these assumptions can be constrained by experimental evidence. All models simulated increased terrestrial carbon pools resulting from CO2 enrichment, though there was substantial variability in quasi-equilibrium carbon sequestration and rates of change. In two of two models that assume that plant nitrogen uptake is solely a function of soil nitrogen supply, the net primary production response to elevated CO2 became progressively nitrogen limited. In four of five models assuming that nitrogen uptake is a function of both soil nitrogen supply and plant nitrogen demand, elevated CO2 led to reduced ecosystem nitrogen losses and thus progressively relaxed nitrogen limitation. Many allocation assumptions resulted in increased wood allocation relative to leaves and roots, which reduced the vegetation turnover rate and increased carbon sequestration. In addition, self-thinning assumptions had a substantial impact on carbon sequestration in two models. Accurate representation of nitrogen process dynamics (in particular nitrogen uptake), allocation, and forest self-thinning is key to minimizing uncertainty in projections of future carbon sequestration in response to elevated atmospheric CO2.

Reference: Walker, A. P., S. Zaehle, B. E. Medlyn, M. G. De Kauwe, S. Asao, T. Hickler, W. Parton, D. M. Ricciuto, Y.-P. Wang, D. Wårlind, and R. J. Norby. 2015. “Predicting Long–Term Carbon Sequestration in Response to CO2 Enrichment: How and Why Do Current Ecosystem Models Differ?” Global Biogeochemical Cycles 29(4), 476–95. DOI: 10.1002/2014GB004995. (Reference link)

Contact: Jared DeForest, SC-23, (301) 903-3251, Daniel Stover, SC-23.1, (301) 903-0289
Topic Areas:

  • Research Area: Earth and Environmental Systems Modeling
  • Research Area: Terrestrial Ecosystem Science
  • Research Area: Carbon Cycle, Nutrient Cycling
  • Research Area: Free Air CO2 Enrichment (FACE)

Division: SC-23.1 Climate and Environmental Sciences Division, BER


BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER

Recent Highlights

Aug 24, 2019
New Approach for Studying How Microbes Influence Their Environment
A diverse group of scientists suggests a common framework and targeting of known microbial processes [more...]

Aug 08, 2019
Nutrient-Hungry Peatland Microbes Reduce Carbon Loss Under Warmer Conditions
Enzyme production in peatlands reduces carbon lost to respiration under future high temperatures. [more...]

Aug 05, 2019
Amazon Forest Response to CO2 Fertilization Dependent on Plant Phosphorus Acquisition
AmazonFACE Model Intercomparison. The Science Plant growth is dependent on the availabi [more...]

Jul 29, 2019
A Slippery Slope: Soil Carbon Destabilization
Carbon gain or loss depends on the balance between competing biological, chemical, and physical reac [more...]

Jul 15, 2019
Field Evaluation of Gas Analyzers for Measuring Ecosystem Fluxes
How gas analyzer type and correction method impact measured fluxes. The Science A side- [more...]

List all highlights (possible long download time)