Nitrous oxide fluxes over establishing biofuel crops: Characterization of temporal variability using the cross-wavelet analysis

Authors: ZERI, MARCELO - National Early Warning And Monitoring Centre Of Natural Disasters (CEMADEN); YANG, WENDY - Benedictine University Of Illinois; CUNHA-ZERI, GISLEINE - Space Research Institute; GIBSON, CHRISTY - University Of Illinois; Bernacchi, Carl

Submitted to: Global Change Biology Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2020
Publication Date: 9/1/2020
Citation: Zeri, M., Yang, W.H., Cunha-Zeri, G., Gibson, C.D., Bernacchi, C.J. 2020. Nitrous oxide fluxes over establishing biofuel crops: Characterization of temporal variability using the cross-wavelet analysis. Global Change Biology Bioenergy. 12(9):756-770. https://doi.org/10.1111/gcbb.12728.
DOI: https://doi.org/10.1111/gcbb.12728

Interpretive Summary: Greenhouse gases are gases in the atmosphere that absorb heat allowing for the earth to maintain a livable temperature. However, if concentrations of these gases get too high, they can cause warming which is what is driving global warming. Growing agricultural crops influence greenhouse gases. Most notable is the fact that plants take carbon dioxide from the atmosphere and use that carbon dioxide for growth. But nitrous oxide is a greenhouse gas emitted from the soil that comes primarily from applying fertilizers to fields. This research looks at the impact of switching agriculture from traditional Midwestern crops to perennial grasses for bioenergy production on the release of nitrous oxide from the soil. The results show that variation among traditional and bioenergy crops result in very different rates of release of N2O. This research is important to consider the environmental consequences of land use change, and can help to better inform models that attempt to understand how ecosystems function in an agricultural setting.

Technical Abstract: Emissions of nitrous oxide (N2O) over croplands are a major source of greenhouse gases to the atmosphere. The precise accounting of sources of N2O is essential to national and global budgets, as well as the understanding of the spatial and temporal relationships with environmental variables such as rainfall, air and soil temperature, and soil moisture. The objective of this work was to investigate the temporal correlations of N2O fluxes with soil and air temperatures, as well as soil moisture. N2O fluxes were measured over four biofuel crops in Central Illinois during their establishment phase. Measurements were carried out from 2009—2011 using a trace gas analyzer with tunable laser technology. Measurements of concentrations of N2O and CO2 were taken at the center of four plots of maize/soybean rotation, miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum) and a mixture of native prairie plants. Cumulative fluxes indicate an average emission of nitrogen via N2O fluxes on the order of 1.7 kg N ha-1 year-1, in agreement with chamber measurements previously reported for the site. N2O fluxes were associated with peaks in soil and air temperature, and soil moisture, particularly during spring and winter thaws. Cross-wavelet analysis was used to investigate the correlation between N2O fluxes and those variables. Results indicate that N2O fluxes and meteorological variables have significant covariance in time scales ranging from 4 to 32 days. In addition, temporal delays of 1 to 8 days were found in those relationships. Cross wavelet patterns were similar when relating N2O fluxes with soil temperature, air temperature and soil moisture. The temporal patterns of fluxes and environmental variables reported here support the modelling of emissions and highlight the importance of considering the timing of fluxes in relation to trends in meteorological variables.