Bioenergy crops have the potential to mitigate greenhouse gas (GHG) emissions and be assumed as a “neutral” energy for GHG emission. However, However, there remain many uncertainties on the “climate neutrality” of biofuel crops, especially the emission of carbon dioxide emission during and after land use change (LUC). During land use conversion, CO2 releases from the agricultural system primarily through soil respiration (R) to the atmosphere and diminishes over time before reaching a new equilibrium. The amount of carbon emission and the payback time depends several factors such as land use history, crop type, and management practices.
To understand the underline mechanisms regulating soil respiration and its two components -- autotrophic (Ra) and heterotrophic (Rh) respiration, we conducted research in Kellogg Biological Station, MI. Two types of land use histories (brome grass under Conservation Reserve Program (CRP) and corn-soybean rotation farms (AGR)) were converted to three no-tillage crops (corn (C), switchgrass (Sw) and local prairie matrix (Pr)), respectively, in addition to a non-disturbed CRP reference site in 2010. Rs, with microclimate variables (i.e., soil temperature (Ts) and soil moisture (VWC)) were monitored biweekly during growing season from the second year after land use conversion. The results represent the different seasonal patterns between annual and perennial crops and both the LUH and crop types affect the relationship between soil respirations and soil temperature.