Seasonal greenhouse gases fluxes from monoculture and mixed native grasslands in the Southern Plains, USA

Authors: PETERSON, BREKKE - FORMER ARS EMPLOYEE; STARKS, PATRICK; STEINER, JEAN - KANSAS STATE UNIVERSITY

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2021
Publication Date: 12/3/2021
Citation: Peterson, B.L., Starks, P.J., Steiner, J.L. 2021. Seasonal greenhouse gases fluxes from monoculture and mixed native grasslands in the Southern Plains, USA. Agrosystems, Geosciences & Environment. 4:e20227. https://doi.org/10.1002/agg2.20227.
DOI: https://doi.org/10.1002/agg2.20227

Interpretive Summary: Agriculture is a net source of atmospheric greenhouse gases (GHG), primarily carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). Regional and management-specific research is needed to ultimately understand the drivers to reduce these emissions. We established research on four Great Plains grassland sites: native prairie and a perennial monoculture sites at the USDA-ARS Grazinglands Research Laboratory, El Reno, OK; a native prairie site at Noble Research Institute, Ardmore, OK; and a native prairie site at Oklahoma State University’s Range Research Station, Marena, OK. Greenhouse gases, along with soil properties were measured bi-weekly and summed by season in 2015 and 2016. These grassland sites were sources of CO2 and N2O emissions, but, importantly, all sites were sinks for CH3, particularly in diverse native sites. In spring, CO2 was driven by soil water content, soil temperature and soil N. N2O flux was highest in the fertilized monoculture pasture. Fluxes of the GHGs were driven by primarily by water content, soil nitrate, soil temperature, and ammonia content. By better understanding GHG fluxes and the abiotic and biotic drivers, we can identify management options to foster C sequestration, increase N use efficiency, and mitigate the GHG footprint for these forage-based systems.

Technical Abstract: Agricultural practices have been linked to soil carbon (C) and nitrogen (N) stores through exchanges with the atmosphere in the form of greenhouse gases (GHG) of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, regional and management-specific research is needed to ultimately understand the base drivers of these atmosphere-warming molecules. We established research on four grassland sites: a native, mixed-species warm-season site and a non-native warm-season grass species site at the Grazinglands Research Laboratory at El Reno, OK; a native, mixed-species warm-season site at Noble Research Institute’s Oswalt Ranch in Ardmore, OK; and a native, mixed-species warm-season site at Oklahoma State University’s Range Research Station at Marena, OK. Greenhouse gases, along with soil properties were measured bi-weekly and summed by season in 2015 and 2016. A comparison of GHGs to soil variables indicated that mineralization of soil nutrients mediated GHG fluxes. The sites were sources of CO2 and N2O emissions, but sinks for CH3, particularly in diverse native sites. In spring, CO2 was driven by soil water content, soil temperature and soil N. N2O flux was highest in the fertilized monoculture pasture. Fluxes of the GHGs were driven by primarily by water content, soil nitrate, soil temperature, and ammonia content. By better understanding GHG fluxes and the abiotic and biotic drivers, we can identify management options to foster C sequestration, increase N use efficiency, and mitigate the GHG footprint for these forage-based systems.