Quantification of net greenhouse gases emissions from U.S. croplands using data-model integration

Authors: YOU, YONGFA - Auburn University; TIAN, HANQIN - Boston College; PAN, SHUFEN - Auburn University; BATCHELOR, WILLIAM - Auburn University; CHENG, BO - Auburn University; HUI, DAFENG - Tennessee State University; LI, XIAOYONG - Auburn University; LIANG, XIN-ZHONG - University Of Maryland; LU, CHAOQUN - Iowa State University; PAN, NAIQING - Auburn University; Prior, Stephen - Steve; SHI, HAO - Auburn University

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 8/3/2022
Publication Date: 12/14/2022
Citation: You, Y., Tian, H., Pan, S., Batchelor, W.D., Cheng, B., Hui, D., Li, X., Liang, X., Lu, C., Pan, N., Prior, S.A., Shi, H. 2022. Quantification of net greenhouse gases emissions from U.S. croplands using data-model integration [ABSTRACT]. American Geophysical Union (AGU) Fall Meeting: Science Leads the Future. Chicago IL. December 12-16.

Interpretive Summary:

Technical Abstract: Agriculture plays a dual role in regulating the Earth’s climate through sequestering soil organic carbon (SOC) and releasing non-CO2 greenhouse gases (GHGs) (i.e., nitrous oxide (N2O) and methane (CH4)). Most previous studies on agricultural climate change mitigation focused on either individual GHGs or SOC, which ignored the trade-offs between SOC sequestration and non-CO2 GHG emissions. Here, we quantified the magnitude and spatiotemporal variations of the net soil GHG emissions (i.e., the balance of SOC sequestration and non-CO2 GHG emissions) from U.S. croplands driven by multiple environmental changes during 1960-2018, using a model-data integration approach. Specifically, a process-based terrestrial biosphere model, Dynamic Land Ecosystem Model v4.0 (DLEM v4.0), was used to perform regional simulations, and a meta-analysis was conducted to compile field observations of SOC sequestration rate and N2O and CH4 emissions to calibrate, validate, and corroborate model simulations. Results show that DLEM can well simulate the magnitudes of site-scale SOC sequestration rate and N2O and CH4 emission rates under various agricultural management practices and environmental conditions, with normalized root mean square errors of 18%, 9%, and 5%, respectively. The average SOC sequestration rate of U.S. croplands from 1960 to 2018 was estimated to be 21.6 Tg C yr-1, and the average emission rates of N2O and CH4 were 0.39 Tg N yr-1 and 0.21 Tg C yr-1, respectively. When translated into global warming potential, the simulated average net GHG emission rate of U.S. croplands was 113.3 Tg CO2-eq yr-1. In addition, the spatial pattern of net soil GHG emissions was highly heterogeneous, with hotspots in the Midwest and Mississippi Delta regions, possibly due to the intensified management practices such as nitrogen fertilization in corn fields and continuous irrigation in rice fields. Our study highlights the importance of simultaneous quantification of SOC sequestration and non-CO2 GHG emissions in developing effective agricultural climate change mitigation measures and assessing regional climate impacts.