Concern over the increase in atmospheric concentration of carbon dioxide (CO₂) from human activities and the resultant impact on global warming led to the search for strategies for mitigating the threat of global climate change. One of the options for CO₂ mitigation is to establish short-rotation intensive culture (SRIC) systems such as hybrid poplar plantations on agricultural lands. The fast-growing and high-yielding nature of hybrid poplars allows large amounts of carbon (C) to be sequestered in long-term storage pools, i.e., wood biomass and soil pools. Although the potential of short-rotation plantations to sequester C is well recognized, there is still a need to determine the sources and amounts of C loss from these systems. Carbon emissions from a two- and nine-year-old hybrid poplar plantation were determined and compared with other land-uses i.e. annual cropping, pastureland, and native aspen forest in this study. More specifically, soil surface and vertical profile fluxes of CO₂ from autotrophic and heterotrophic sources were quantified over the growing seasons of 2006 and 2007. The interaction between temperature, moisture, and other biophysical variables in relation to soil respirations were examined and are reported in the study.