Simulating climate change effects on soil carbon dynamics in a soybean-maize ecosystem: Using improved CO2 emission and transport models

Authors: SUN, WENGUANG - University Of Nebraska; Fleisher, David; Timlin, Dennis; RAY, CHITTARANJAN - University Of Nebraska; WANG, ZHUANGJI - University Of Maryland; BEEGUM, SAHILA - University Of Nebraska; Reddy, Vangimalla

Submitted to: European Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2024
Publication Date: 6/17/2024
Citation: Sun, W., Fleisher, D.H., Timlin, D.J., Ray, C., Wang, Z., Beegum, S., Reddy, V. 2024. Simulating climate change effects on soil carbon dynamics in a soybean-maize ecosystem: Using improved CO2 emission and transport models. European Journal of Agronomy. 159. Article e127226. https://doi.org/10.1016/j.eja.2024.127226.
DOI: https://doi.org/10.1016/j.eja.2024.127226

Interpretive Summary: Air temperatures and atmospheric carbon dioxide (CO2) levels are projected to continue to increase. These climate changes may alter the amount of carbon being stored in the soil, which can be measured as soil organic carbon (SOC). This SOC is an important metric which relates to the general health of the soil. This value can change due to differences in crop production as well as a loss of soil carbon that is associated with microbial activity and measured as respiration. Understanding how climate variables influence soil respiration is very important so that scientists can more accurately predict, understand, and learn how to mitigate potential climate change impacts on soil health. Many scientific tools are used to simulate these impacts but need to be improved. We developed new mathematical expressions and linked them with sophisticated crop, soil, and climate models to study effects of global warming on SOC changes in a maize-soybean cropping system in Illinois, USA. The improved models were accurate when compared with existing observations. Future changes in temperature were shown to lead to long-term declines in SOC. However, projected increases in CO2 can offset this loss. The development of these improved models, and the simulated results, will benefit farmers and scientists interested in identifying strategies to improve management of agricultural systems associated with soil health.

Technical Abstract: Climate change has been reported to significantly affect soil carbon storage, but it remains unclear how to predict the effect of high temperatures and elevated atmospheric carbon dioxide concentration (CO2) on soil organic carbon (SOC) dynamics. We used two process-based crop models, GLYCIM and MAIZSIM, to evaluate the effects of climatic change on SOC accumulation in a maize-soybean cropping system. Models were improved with methods to account for tillage, surface residue decomposition, and soil respiration. Data from a 3-year free-air-CO2-enrichment (FACE) experiment from Illinois, USA were used for calibration and validation. Model performance was then evaluated against observed crop yield and SOC in this long-term cropping system from 1900-2020. The crop models accurately matched the soil CO2 fluxes and surrounding environment data associated with plant roots and rhizosphere respiration (root mean square error (RMSE), 11.7 - 16.0 kg C per hectare per day), soil heterotroph respiration (RMSE, 7.0 -11.3 kg C per hectare per day), whole soil respiration (RMSE, 6.2 -9.3 kg C per hectare per day), soil water content (RMSE, 7.0 -11.3 percent), and soil temperature (RMSE, 7.0 -11.3 oC). Our model projections, using an ensemble of five general circulation models (GCMs) from the latest Sixth Coupled Model Intercomparison Project (CMIP6), suggested that future warming temperatures would cause long term declines in SOC by the end of the 21st century, with losses of 6.0 % and 14.6 % under different projected greenhouse emission pathways. Incorporating the effects of elevated CO2 in the study showed a beneficial response with SOC content increasing by 5.0 - 6.2%. This study highlights the importance of linking controlled experiments, long-term field observations and future climate projections with process-based crop models for SOC sequestration assessment and impact in maize-soybean cropping systems.