Does elevated atmospheric CO2affect soil carbon burial and soil weathering in a forest ecosystem?

Miquel A Gonzalez-Meler; Armen Poghosyan; Yaniria Sanchez-de Leon; Eduardo Dias de Olivera; Richard J Norby; Neil C Sturchio

doi:10.7717/peerj.5356

Does elevated atmospheric CO₂affect soil carbon burial and soil weathering in a forest ecosystem?

PeerJ. 2018 Jul 27:6:e5356. doi: 10.7717/peerj.5356. eCollection 2018.

Authors

Miquel A Gonzalez-Meler¹, Armen Poghosyan^{1

2}, Yaniria Sanchez-de Leon^{1

3}, Eduardo Dias de Olivera¹, Richard J Norby⁴, Neil C Sturchio^{1

5}

Affiliations

¹ Department of Biological Sciences and Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA.
² Space Center, Skolkovo Institute of Science and Technology, Moscow, Russia.
³ Department of Agro-environmental Sciences, Universidad de Puerto Rico at Mayaguez, Mayaguez, Puerto Rico.
⁴ Environmental Science Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁵ Department of Earth and Environmental Sciences, University of Delaware, Newark, DE, USA.

Abstract

Most experimental studies measuring the effects of climate change on terrestrial C cycling have focused on processes that occur at relatively short time scales (up to a few years). However, climate-soil C interactions are influenced over much longer time scales by bioturbation and soil weathering affecting soil fertility, ecosystem productivity, and C storage. Elevated CO₂can increase belowground C inputs and stimulate soil biota, potentially affecting bioturbation, and can decrease soil pH which could accelerate soil weathering rates. To determine whether we could resolve any changes in bioturbation or C storage, we investigated soil profiles collected from ambient and elevated-CO₂plots at the Free-Air Carbon-Dioxide Enrichment (FACE) forest site at Oak Ridge National Laboratory after 11 years of ¹³C-depleted CO₂ release. Profiles of organic carbon concentration, δ¹³C values, and activities of ¹³⁷Cs, ²¹⁰Pb, and ²²⁶Ra were measured to ∼30 cm depth in replicated soil cores to evaluate the effects of elevated CO₂ on these parameters. Bioturbation models based on fitting advection-diffusion equations to ¹³⁷Cs and ²¹⁰Pb profiles showed that ambient and elevated-CO₂ plots had indistinguishable ranges of apparent biodiffusion constants, advection rates, and soil mixing times, although apparent biodiffusion constants and advection rates were larger for ¹³⁷Cs than for ²¹⁰Pb as is generally observed in soils. Temporal changes in profiles of δ¹³C values of soil organic carbon (SOC) suggest that addition of new SOC at depth was occurring at a faster rate than that implied by the net advection term of the bioturbation model. Ratios of (²¹⁰Pb/²²⁶Ra) may indicate apparent soil mixing cells that are consistent with biological mechanisms, possibly earthworms and root proliferation, driving C addition and the mixing of soil between ∼4 cm and ∼18 cm depth. Burial of SOC by soil mixing processes could substantially increase the net long-term storage of soil C and should be incorporated in soil-atmosphere interaction models.

Keywords: Bioturbation; Elevated CO2; Isotope; Soil C; Temperate forest; cesium-137; lead-210.

Grants and funding

This work was supported by the United States National Science Foundation grant DEB-0919276 to Miquel Angel Gonzalez-Meler and Yaniria Sánchez-de León. Dr. Sánchez-de León was also supported by a NSF-ADVANCE postdoctoral fellowship. The Oak Ridge National Laboratory FACE site was supported by the United States Department of Energy, Office of Science, Biological and Environmental Research program. Oak Ridge National Laboratory is managed by University of Tennessee-Battelle, LLC for the United States Department of Energy under contract DE-AC05-00OR22725. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.