TY - JOUR
T1 - Grazing alters net ecosystem C fluxes and the global warming potential of a subtropical pasture
AU - Gomez-Casanovas, Nuria
AU - Delucia, Nicholas J.
AU - Bernacchi, Carl J.
AU - Boughton, Elizabeth H.
AU - Sparks, Jed P.
AU - Chamberlain, Samuel D.
AU - Delucia, Evan H.
N1 - Funding Information:
We thank John Garrett, MacArthur Agro-ecology Research Center (MAERC) interns (Chelsea Gowton, Vi Bui, Megan Foster, Jessie Franks, Colleen Smith, Diana Jaramillo, Lara Jansen, Federico Borghesi, Eric Behrens, and Katie Nigro), and Earl Keel for field assistance, and Melissa Wasson, Derick Carnazzola, and Jiwoong Hong for laboratory assistance. We are grateful to Julia Maki, and the rest of the staff at MAERC for site access, lodging, transportation, and continued support in the field. This research was funded by the Energy Biosciences Institute (EBI; University of Illinois at Urbana-Champaign, Urbana, Illinois, USA), the U.S. Department of Energy SunGrant Program (DE-FG36-08GO88073), and the U.S. Department of Agriculture NIFA (Project No. 2016-67019-24988).
Funding Information:
This research was funded by the Energy Biosciences Institute (EBI; University of Illinois at Urbana-Champaign, Urbana, Illinois, USA), the U.S. Department of Energy SunGrant Program (DE-FG36-08GO88073), and the U.S. Department of Agriculture NIFA (Project No. 2016-67019-24988).
Publisher Copyright:
© 2017 by the Ecological Society of America.
PY - 2018/3
Y1 - 2018/3
N2 - The impact of grazing on C fluxes from pastures in subtropical and tropical regions and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO2 and CH4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet-dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (Reco) and gross primary productivity (GPP). As the decrease in Reco was larger than the reduction in GPP, grazing consistently increased the net CO2 sink strength of subtropical pastures (55, 219 and 187 more C/m2 in 2013, 2014, and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH4 emissions in grazed relative to ungrazed pasture (27-80%). Unlike temperate, arid, and semiarid pastures, where differences in CH4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH4 emissions can be greater than CH4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO2 sink strength.
AB - The impact of grazing on C fluxes from pastures in subtropical and tropical regions and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO2 and CH4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet-dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (Reco) and gross primary productivity (GPP). As the decrease in Reco was larger than the reduction in GPP, grazing consistently increased the net CO2 sink strength of subtropical pastures (55, 219 and 187 more C/m2 in 2013, 2014, and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH4 emissions in grazed relative to ungrazed pasture (27-80%). Unlike temperate, arid, and semiarid pastures, where differences in CH4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH4 emissions can be greater than CH4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO2 sink strength.
KW - CH
KW - cattle
KW - flooded land
KW - grassland
KW - methane
KW - net ecosystem CO exchange
KW - net ecosystem productivity
KW - pasture
KW - subtropical
KW - tropical
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U2 - 10.1002/eap.1670
DO - 10.1002/eap.1670
M3 - Article
C2 - 29280238
AN - SCOPUS:85042700630
SN - 1051-0761
VL - 28
SP - 557
EP - 572
JO - Ecological Applications
JF - Ecological Applications
IS - 2
ER -