Examining surface energy and moisture balance changes associated with land conversion from annual to perennial biofuel crops

albedo, bioenergy, biofuel crops, corn, land-use change, miscanthus, radiative forcing, snow, soybean, switchgrass, CO2, heat, Agro-IBIS, transpiration, soil evaporation, evapotranspiration, water balance, off-axis integrated cavity spectrometry, Keeling plot

Miller, Jesse

关键词: albedo, bioenergy, biofuel crops, corn, land-use change, miscanthus, radiative forcing, snow, soybean, switchgrass, CO2, heat, Agro-IBIS, transpiration, soil evaporation, evapotranspiration, water balance, off-axis integrated cavity spectrometry, Keeling plot;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/101014/MILLER-DISSERTATION-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Population growth and shifts in the global economy are creating greater demand for food, fiber, and fuel.These demands are driving land use changes (LUC) associated with expanding food production and the search for renewable energy.Second-generation cellulosic biofuel feedstocks are being pursued as part of the solution to diversifying both the agro-economic and renewable energy sectors.This land conversion is expected to alter the surface energy balance via albedo changes and shifts in the partitioning of energy between sensible and latent heat fluxes.The degree to which albedo will shift is uncertain, as is the feedback this shift may have on regional climate.This thesis examines how land conversion from the traditional annual crops maize (Zea mays) and soybean (Glycine max) to perennial biofuel crops miscanthus (Miscanthus × giganteus) and switchgrass (Panicum virgatum) alters surface radiation and water balance and the implications of these changes on large-scale energy and water budgets.The goals of this research are to: 1) quantify changes to albedo from transitioning from annual row crops to perennial biofuel crops and 2) implement these changes into a biophysical model in order to simulate the impact that a variety of land management strategies could have on regional climate.Albedo of perennial grasses and traditional row crops was measured over multiple years and multiple locations around central Illinois.Results show that perennial biofuel crops had an overall higher albedo than current agricultural crops but there was a strong seasonal pattern.During the growing season perennials had higher albedo than row crops, with miscanthus having the highest followed by switchgrass then row crops.Averaged over the course of the study, crop albedos had the opposite trend during winter, though results were not statistically significant due to intra-annual variations in snow cover.When snow covered the ground, harvested annual row crop fields had very high albedo whereas non-harvested perennial fields gave more moderate values.Following harvest, the albedo of the perennials did not differ substantially from row crops.Overall, these albedo measurements reveal that planting perennial biofuel crops resulted in a large reduction in radiative forcing to the surface energy balance.These albedo measurements along with other relevant observations were implemented into the Agro-IBIS model to investigate potential biophysical impacts associated with implementing climate-smart management techniques such as utilizing crops with longer growing seasons, converting to no-till agriculture, and planting perennial biofuel crops.Key findings from these scenarios show: 1) a decrease in net surface radiation caused by the increased crop residue left behind from no-till agriculture, 2) lower net surface radiation from expanding the area covered by perennial crops, and 3) a reduction of the sensible to latent heat flux ratio and suppressed soil temperatures caused by planting crops that can better utilize the longer growing season that is expected due to global warming.The findings presented here show that the expansion of perennial biofuel crops will have significant biogeophysical impacts on the surface energy and water balance and will generally cool the surface of the earth.Additionally, perennial crops are well suited to being part of a diverse portfolio of climate-smart land management schemes.