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

Abstract

AbstractAgricultural practices have been linked to soil carbon (C) and nitrogen (N) stores through exchanges with the atmosphere in the form of greenhouse gases (GHGs) of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, regional and management‐specific research is needed to ultimately understand the 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 biweekly and summed by season in 2015 and 2016. A comparison of GHGs with soil variables indicated that mineralization of soil nutrients mediated GHG fluxes. The sites were sources of CO2 and N2O emissions, but sinks for CH4, particularly in diverse native grassland sites. In spring, CO2 emissions were driven by soil water content, soil temperature, and soil N. The N2O emissions were highest in the fertilized monoculture pasture. Overall, 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 and mitigate the GHG footprint for these forage‐based systems.