Unraveling the effects of management and climate on carbon fluxes of U.S. croplands using the USDA Long-Term Agroecosystem (LTAR) network

Authors: Menefee, Dorothy; Scott, Russell - Russ; ABRAHA, MICHAEL - Michigan State University; Alfieri, Joseph; Baker, John; Browning, Dawn; CHEN, JIQUAN - Michigan State University; Gonet, Jeffery; Johnson, Jane; MILLER, GRETCHEN - Texas A&M University; Nifong, Rachel; ROBERTSON, PHIL - Michigan State University; RUSSEL, ERIC - Washington State University; Saliendra, Nicanor; Schreiner-Mcgraw, Adam; SUYKER, ANDREW - University Of Nebraska; Wagle, Pradeep; Wente, Christopher - Chris; White, Paul; Smith, Douglas

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2022
Publication Date: 9/16/2022
Citation: Menefee, D.S., Scott, R.L., Abraha, M., Alfieri, J.G., Baker, J.M., Browning, D.M., Chen, J., Gonet, J.M., Johnson, J.M., Miller, G.R., Nifong, R.L., Robertson, P., Russel, E.R., Saliendra, N.Z., Schreiner-Mcgraw, A.P., Suyker, A., Wagle, P., Wente, C.D., White Jr, P.M., Smith, D.R. 2022. Unraveling the effects of management and climate on carbon fluxes of U.S. croplands using the USDA Long-Term Agroecosystem (LTAR) network. Agricultural and Forest Meteorology. 326. Article 109154. https://doi.org/10.1016/j.agrformet.2022.109154.
DOI: https://doi.org/10.1016/j.agrformet.2022.109154

Interpretive Summary: A summary analysis of eddy covariance carbon flux data across LTAR cropland sites was performed. Carbon flux was compared to climatic variables and management practices. Climate, location, tillage practices, and crop selection were all significantly related to cropland carbon flux.

Technical Abstract: Understanding the carbon flux dynamics from a broad range of agricultural systems has the potential to improve our ability to increase carbon sequestration while maintaining crop yields. Short-term, single-location studies have limited applicability, but long-term data from a network of many locations is needed for a broader understanding across gradients of climate and management choices. Therefore, this analysis examines eddy covariance measured carbon dioxide (CO2) fluxes from cropland sites across the United States Department of Agriculture’s Long-Term Agroecosystem Research (LTAR). The dataset was collected between 2001 and 2020, spanning 13 sites for a total of 182 site-years. Average seasonal patterns of net ecosystem CO2 exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) were determined, and subsequent regression analysis on these “flux climatologies” was used to identify relationships to mean annual temperature (MAT), mean annual precipitation (MAP), cropping systems, and management practices. At rainfed sites, carbon fluxes were better correlated with MAP (r2 = 0.5) than MAT (r2 = 0.22). Net carbon balance was different among cropping systems (p < 0.001), with the greatest net carbon uptake occurring in sugarcane (Saccharum spp. hybrids ) and the least in soybean (Glycine max) fields. Crop type had a greater effect on carbon balance than irrigation management at a Nebraska site. Across cropping systems, grain crops often had higher GPP and were more likely to have net uptake when compared to legume crops. This multi-site analysis highlights the potential of the LTAR network to further carbon flux research using eddy covariance measurements.