Climate regulation ecosystem services of biofuels: a new paired flux tower study comparing loblolly pine and switchgrass ecosystems

Land-conversion for biofuel use is a globally widespread land-use transition and is an explicit component of future scenarios developed to address climate change. Biofuels create climate benefits by potentially providing a fuel source that does not require burning fossil fuels. However, land conversion for biofuels can also alter the climate directly by modifying ecosystems' capacity to transfer energy to the atmosphere. Ideally, these modifications to the energy balance enhance the climate benefits associated with reducing CO2 in the atmosphere. But the modifications to energy balance could counteract the benefits of CO2 uptake, especially if the biofuel ecosystem is darker, thus reflecting less energy, than the ecosystem prior to biofuel establishment. To address the need for observations that quantify the net influence of land management for biofuels on climate, we established a new paired flux tower study (Sweet Briar Land-Atmosphere Research Station) that compares the carbon and energy balance between a managed loblolly pine forest and switchgrass field in Central Virginia, USA. Here we present the first year of observations from the paired sites. Our preliminary analysis indicates that the lower albedo of the pine compared to the switchgrass results in increased net radiation. This increased net radiation in pine is dissipated through elevated sensible and latent heat fluxes. The ratio of sensible to latent heat fluxes was higher in the pines than the switchgrass. Net ecosystem exchange of carbon dioxide over the first growing season was higher for the pine that the switchgrass. These data, combined with land-surface modeling, aim to help inform our understanding of how decisions to establish specific ecosystem types for supplying biofuel feedstocks influence local, regional, and global climate.