Impacts of biofuel crops on atmospheric volatile organic composition and potential consequences for global climate change

The introduction of new crops to agroecosystems can change the chemical composition of the atmosphere by altering the bouquet of plant-derived biogenic volatile organic compounds (BVOCs). BVOCs are low molecular weight secondary metabolites that are generally used by plants for defense, pollination and communication purposes. They also influence the atmosphere as potential greenhouse gases and precursors of particulate matter. In this study, we compared BVOC emissions from three potential biofuel crops and estimated their theoretical impacts on bioenergy agroecosystems. The crops chosen were miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum) and an assemblage of prairie species (mix of ~28 species). The concentration of BVOCs was different within and above plant canopies. All crops produced higher levels of emissions at the upper canopy level. Miscanthus produced lower amounts of volatiles compared to other grasses. The chemical composition of volatiles differed significantly across all three plant canopies. BVOCs from miscanthus were depleted in terpenoids relative to the other vegetation types. The carbon flux via BVOC emissions, calculated using the flux-gradient method, was significantly higher in the prairie assemblage compared to miscanthus and switchgrass. The BVOC carbon flux was approximately three orders of magnitude lower than the net fluxes of carbon measured over the same fields by eddy covariance systems. Extrapolation of our findings to the landscape scale leads us to suggest that the widespread adoption of biofuel crops can potentially alter the composition of BVOCs in the atmosphere, thereby influencing its warming potential, the formation of atmospheric particulates and interactions between plants and arthropods.