NW Ohio Flux Cluster

My Ph.D. research focused on the response and biophysical regulation of ecosystem carbon fluxes to recent climatic variability and anomaly in contrasting ecosystems in Northwest Ohio (i.e., an oak-dominant forest, a freshwater marsh, and a soybean-wheat cropland). Our research deployed a cluster of eddy-covariance towers in NW Ohio and used these concurrent, continuous measurements to disentangle the biological and physical modulation. Collaboratively, I also participated in the studies that investigated the interannual variability of carbon and water fluxes at the oak-dominated forest and the pioneer studies that explored and measured carbon and water fluxes over western Lake Erie. My key contributions are summarized as follows.

I developed a Bayesian hierarchical model to partition the interannual variation of ecosystem photosynthesis and respiration that resulted directly from the short-term environmental forcing and indirectly from the changes of ecosystem functional traits (e.g., structural, physiological, and phenological traits) (Chu et al., 2016). The study suggested that the indirect effects mainly drove year-to-year changes in carbon fluxes, and most importantly, the ecosystem’s response to climate was strongly site-specific.
I initiated and conducted the first full carbon balance study for a freshwater marsh where the vertical gaseous (CO2 and CH4) and lateral hydrologic fluxes (dissolved and particulate organic carbon) have been simultaneously measured for multiple years (Chu et al., 2014; 2015). The studies highlighted the importance of freshwater marshes for their high CH4 emission and substantial lateral hydrologic carbon inflows/outflows. These ecosystems are potentially efficient in turning over and releasing newly fixed carbon (allochthonous and autochthonous) as CH4 and should be carefully addressed in the regional carbon budget.
I participated in a series of studies targeting the long-term oak-dominated forest site, where we deciphered and disentangled the multiple drivers and mechanisms regulating the interannual variability of carbon and water fluxes (Ouyang et al., 2014; Xie et al., 2014a; 2014b; 2016).
I also worked collaboratively in the pioneer studies of carbon and water fluxes over western Lake Erie. Our studies showed that lake evaporation returned approximately 90% of annual rainfall to the atmosphere (Shao et al., 2015). Pronounced seasonal patterns in surface energy fluxes were observed with a 2-month lag in lake evaporation from the net radiation due to the lake's heat storage (Shao et al., 2020). Lake Erie generally acts as a minor carbon source to the atmosphere, but large-scale intensive algal blooms could reduce short-term carbon emissions (Ouyang et al., 2017).

Relevant Publication

Shao, C., J. Chen, H. Chu, C. A. Stepien, and Z. Ouyang. (2020) Intra- and inter-annual dynamics of evaporation over western Lake Erie. Earth and Space Science. 7, e2020EA001091, https://doi.org/10.1029/2020EA001091
Ouyang, Z., C. Shao, H. Chu, R. Becker, T. Bridgeman, C. Stepien, R. John, and J. Chen. (2017) The effect of algal blooms on carbon emissions in western Lake Erie: An integration of remote sensing and eddy covariance measurements. Remote Sensing, 9(1): 44, https://doi.org/10.3390/rs9010044
Chu, H., J. Chen, J. F. Gottgens, A. R. Desai, Z. Ouyang, and S. Qian. (2016) Response and biophysical regulation of carbon dioxide fluxes to climate variability and anomaly in contrasting ecosystems in northwestern Ohio, USA. Agricultural and Forest Meteorology, 220: 50-68, https://doi.org/10.1016/j.agrformet.2016.01.008
Xie, J., J. Chen, G. Sun, T. Zha, B. Yang, H. Chu, J. Liu, S. Wan, C. Zhou, H. Ma, C. P.-A. Bourque, C. Shao, R. John, and Z. Ouyang. (2016) Ten-year variability in ecosystem water use efficiency in an oak-dominated temperate forest under a warming climate. Agricultural and Forest Meteorology, 218-219: 209-217, https://doi.org/10.1016/j.agrformet.2015.12.059
Shao, C., J. Chen, C. A. Stepien, H. Chu, T. Bridgeman, K. Czajkowski, R. Becker, Z. Ouyang, and R. John. (2015) Diurnal to annual changes in latent, sensible heat and CO2 fluxes over a Laurentian Great Lake: A case study in western Lake Erie. Journal of Geophysical Research: Biogeosciences, 120(8): 1587-1604, https://doi.org/10.1002/2015JG003025 (AGU EOS Research Spotlight (2015), 96, https://doi.org/10.1029/2015EO037667)
Chu, H., J. F. Gottgens, J. Chen, G. Sun, A. R. Desai, Z. Ouyang, C. Shao, and K. Czajkowski. (2015) Climatic variability, hydrologic anomaly, and methane emission can turn productive freshwater marches into net carbon sources. Global Change Biology, 21(3): 1165-1181. https://doi.org/10.1111/gcb.12760
Ouyang, Z., J. Chen, R. Becker, H. Chu, J. Xie, C. Shao, and R. John. (2014) Disentangling the confounding effects of PAR and air temperature on net ecosystem exchange in time and scale. Ecological Complexity, 19: 46-58. https://doi.org/10.1016/j.ecocom.2014.04.005
Chu, H., J. Chen, J. F. Gottgens, Z. Ouyang, R. John, K. Czajkowski, and R. Becker. (2014) Net ecosystem methane and carbon dioxide exchanges in a Lake Erie coastal marsh and a nearby cropland. Journal of Geophysical Research: Biogeosciences, 119(5): 722-740. https://doi.org/10.1002/2013JG002520
Xie, J., J. Chen, G. Sun, H. Chu, A. Noormets, Z. Ouyang, R. John, S. Wan, and W. Guan. (2014). Long-term variability and environmental control of the carbon cycle in an oak-dominated temperate forest. Forest Ecology and Management, 313: 319-328. https://doi.org/10.1016/j.foreco.2013.10.032
Xie, J., G. Sun, H. Chu, J. Liu, S. G. McNulty, A. Noormets, R. John, Z. Ouyang, T. Zha, H. Li, W. Guan, and J. Chen. (2014). Long-term variability in water budget and its controls in an oak-dominated temperate forest. Hydrological Processes, 28(25): 6054-6066. https://doi.org/10.1002/hyp.10079
Deal, M.W., J. Xu, R. John, T. Zenone, J. Chen, P. Jasrotia, K. Kahmark, H. Chu, J. Bossenbroek, and C. Mayer. (2013). Net primary production in three bioenergy crop systems following land conversion. Journal of Plant Ecology, 7(6): 1-10. https://doi.org/10.1093/jpe/rtt057

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