Lei, C. 2022. The analysis of albedo on bioenergy crops: Assessment for climate and global warming impact. Dissertation, Michigan State University, East Lansing MI.

What if the production and expansion of bioenergy crops was realized? What bioenergy crops would be planted? Which crops would be sustainable? How would bioenergy affect landscape dynamics, surface reflectivity and global warming impact? These core questions are investigated in this dissertation by investigating the effects of agronomic practices, climate and crop-species on albedo in southwest Michigan.

Albedo changes can be quantified in terms of global radiative forcing (RF), which can be positive or negative, correlating to carbon emissions or sequestrations in biofuel ecosystems respectively. With an overarching hypothesis which aims to understand how albedo is dependent on the landscape (i.e., crop-species type), climate variables (i.e., micrometeorological, temporal, and seasonal) and agricultural practices (i.e., fertilization, stover retention), which in turn affect its global warming impact and the ability to reflect more sunlight back into the atmosphere and sequester carbon. As a result, the Kellogg Biological Station was selected as the study site.

This research analyzes changes in albedo over seven different biofuel crops at the Biofuel Cropping System Experiment (BCSE), situated at the Great Lakes Bioenergy Research Center (GLBRC). This dissertation investigates the radiative forcing associated with each one of the bioenergy scenarios, in order to model the conversion of a landscape into a relatable carbon dioxide equivalent. This CO2 equivalent—called global warming impact (GWI)—allows for a climate impact comparison of potential global warming impact of CO2 emissions from biofuels relative to a reference gas to investigate potential climate warming/cool impacts. This research examined annual row crops of maize and energy sorghum, monoculture perennial grasses of switchgrass and miscanthus, and polyculture perennials of native grasses, early successional grassland and restored prairie bioenergy systems. Each chapter provides a deeper analysis into the spatiotemporal effects of surface reflectivity on biofuel ecosystems and provides an understanding of the total global warming impact of different croplands and their contribution to the energy budget and carbon production.

Results of this research include: 1) a long-term network of towers which effectively measure albedo continuously over multiple biofuel ecosystems, and 2) regionalized instantaneous data from landscapes of candidate bioenergy crops to significantly advance knowledge and understanding in how surface reflectivity affects GWI.

Major findings indicated that albedo observations are an invaluable tool in order to calculate and improve climate models, in order to understand how land use and land cover affects albedo and climate cooling. Perennial grasses provided a sustainable form of climate mitigation by reflecting more solar radiation back into the atmosphere, and can sustainability provide localized cooling while reducing the need for fertilizer input. Finally, an overall cooling effect from modeling the conversion of historical landscape forest and modern landscapes of maize over a three-year study period to candidate different bioenergy crops was found, which indicated a climate warming mitigation from long-term increased surface albedo reflectance.

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