Global warming impacts of converting forest into bioenergy croplands - Case study at the Kellogg Biological Station

Cheyenne Lei (1,2,3), Jiquan Chen (1,2,3), G. Philip Robertson (2,4,5)
1 Department of Geography, Environment and Spatial Sciences, Michigan State University, East Lansing, MI 2 DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 3 Center for Global Change and Earth Observations, Michigan State University, East Lansing, MI 4 W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI 5 Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI

Presented at the All Scientist Meeting and Investigators Field Tour (2021-09-23 to 2021-09-23 )

Land use change can directly or indirectly modify biogeophysical properties of the surface affecting surface reflectivity (albedo), which can inherently influence climate through radiative forcing (RF). Understanding how global warming impact (GWI) can estimate carbon cooling/warming effects of albedo-induced GWI when converted from a reference forest to another bioenergy crop is vital to mitigating climate change. In-situ measurements were used to quantify the magnitudes and temporal (i.e., intra- and inter-annual) changes of albedo (∆), RF∆α , and GWI∆α in bioenergy crops of maize, sorghum, switchgrass, miscanthus, native grasses, restored prairie, and early successional bioenergy systems in southwest Michigan from May 2018 to December 2020; a nearby forest was used as a historical reference.

For all biofuel crops, land conversion from forest exhibited a negative net cooling effect, with contributions of annual GWIΔα varying by crop and year. Growing season GWIΔα values closely resembled annual GWIΔα observations, with values during both time scales being significant at p<0.05 from a Tukey post-hoc test. Higher cooling effects were observed during the growing season in early successional, miscanthus, sorghum and switchgrass sites with annual average GWIΔα mitigation observed to be more pronounced in 2020, compared to its preceding years. Seasonal and monthly effects of albedo-induced GWIΔα cooling effects were observed during the summer months of Jun-Sept, with the highest cooling observed in August at an average of -1.06 Mg CO2eq. ha-1 yr-1, with lowest contributions occurring in Nov-December. Our method can be successfully utilized to quantify the radiative effect of albedo change in bioenergy croplands and relate it to climate impact of GHG gases over a 3 year period, in order to identify effective alternative land uses for biofuel energy.

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