Perennial biomass crops are being considered for sustainable energy production and may help ameliorate the effects of global climate change due to their ability to sequester carbon in soil and biomass; however, little is known about the contrasting effects of species composition and management on carbon sequestration.  We investigated net ecosystem productivity (NEP) and carbon stores in a diverse mixture of native grassland species, and a monoculture of switchgrass (Panicum virgatum) established on marginal agricultural land in SW Wisconsin, USA.  These crops were established in 2008, and received a treatment of prescribed fire or no fire in 2009.  To determine the effects of species diversity and prescribed fire on the net ecosystem carbon budget, we estimated carbon stores in above- and belowground biomass and soil, and carbon flux due to respiration from soil and vegetation.   

Results/Conclusions

Preliminary analyses indicate that burning did not affect biomass productivity (above- or belowground), and that average aboveground biomass productivity was 101% greater in switchgrass monocultures than in diverse mixtures (burned or unburned) (p<0.01).  Belowground biomass, total respiration, and total soil carbon did not differ among treatments.  Total carbon sequestered in above- and belowground biomass will also be presented.  We will present a net ecosystem carbon budget for each of our four experimental treatments, thereby evaluating these perennial biomass systems in terms of relative effects on global climate.  This study provides important information for farmers, conservationists, and the energy industry on the impacts of management on the carbon sequestration potential of native biomass crops.