How does elevated ozone reduce methane emissions from peatlands?

TY - JOUR

T1 - How does elevated ozone reduce methane emissions from peatlands?

AU - Toet, Sylvia

AU - Oliver, Viktoria

AU - Ineson, Phil

AU - McLoughlin, Sophie

AU - Helgason, Thorunn

AU - Peacock, Simon

AU - Stott, Andrew W.

AU - Barnes, Jeremy

AU - Ashmore, Mike

N1 - © 2016 Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

PY - 2017/2/1

Y1 - 2017/2/1

N2 - The effects of increased tropospheric ozone (O3) pollution levels on methane (CH4) emissions from peatlands, and their underlying mechanisms, remain unclear. In this study, we exposed peatland mesocosms from a temperate wet heath dominated by the sedge Schoenus nigricans and Sphagnum papillosum to four O3 treatments in open-top chambers for 2.5years, to investigate the O3 impacts on CH4 emissions and the processes that underpin these responses. Summer CH4 emissions, were significantly reduced, by 27% over the experiment, due to summer daytime (8hday-1) O3 exposure to non-filtered air (NFA) plus 35ppb O3, but were not significantly affected by year-round, 24hday-1, exposure to NFA plus 10ppb or NFA plus 25ppb O3. There was no evidence that the reduced CH4 emissions in response to elevated summer O3 exposure were caused by reduced plant-derived carbon availability below-ground, because we found no significant effect of high summer O3 exposure on root biomass, pore water dissolved organic carbon concentrations or the contribution of recent photosynthate to CH4 emissions. Our CH4 production potential and CH4 oxidation potential measurements in the different O3 treatments could also not explain the observed CH4 emission responses to O3. However, pore water ammonium concentrations at 20cm depth were consistently reduced during the experiment by elevated summer O3 exposure, and strong positive correlations were observed between CH4 emission and pore water ammonium concentration at three peat depths over the 2.5-year study. Our results therefore imply that elevated regional O3 exposures in summer, but not the small increases in northern hemisphere annual mean background O3 concentrations predicted over this century, may lead to reduced CH4 emissions from temperate peatlands as a consequence of reductions in soil inorganic nitrogen affecting methanogenic and/or methanotrophic activity.

AB - The effects of increased tropospheric ozone (O3) pollution levels on methane (CH4) emissions from peatlands, and their underlying mechanisms, remain unclear. In this study, we exposed peatland mesocosms from a temperate wet heath dominated by the sedge Schoenus nigricans and Sphagnum papillosum to four O3 treatments in open-top chambers for 2.5years, to investigate the O3 impacts on CH4 emissions and the processes that underpin these responses. Summer CH4 emissions, were significantly reduced, by 27% over the experiment, due to summer daytime (8hday-1) O3 exposure to non-filtered air (NFA) plus 35ppb O3, but were not significantly affected by year-round, 24hday-1, exposure to NFA plus 10ppb or NFA plus 25ppb O3. There was no evidence that the reduced CH4 emissions in response to elevated summer O3 exposure were caused by reduced plant-derived carbon availability below-ground, because we found no significant effect of high summer O3 exposure on root biomass, pore water dissolved organic carbon concentrations or the contribution of recent photosynthate to CH4 emissions. Our CH4 production potential and CH4 oxidation potential measurements in the different O3 treatments could also not explain the observed CH4 emission responses to O3. However, pore water ammonium concentrations at 20cm depth were consistently reduced during the experiment by elevated summer O3 exposure, and strong positive correlations were observed between CH4 emission and pore water ammonium concentration at three peat depths over the 2.5-year study. Our results therefore imply that elevated regional O3 exposures in summer, but not the small increases in northern hemisphere annual mean background O3 concentrations predicted over this century, may lead to reduced CH4 emissions from temperate peatlands as a consequence of reductions in soil inorganic nitrogen affecting methanogenic and/or methanotrophic activity.

KW - C

KW - CH

KW - Mires

KW - Nitrogen

KW - Sedge

KW - Sphagnum papillosum

UR - http://www.scopus.com/inward/record.url?scp=85006754138&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2016.10.188

DO - 10.1016/j.scitotenv.2016.10.188

M3 - Article

AN - SCOPUS:85006754138

SN - 0048-9697

VL - 579

SP - 60

EP - 71

JO - Science of the Total Environment

JF - Science of the Total Environment

IS - 1 Feb 2017

M1 - j.scitotenv.2016.10.188

ER -