Carbon Balance and Evapotranspiration Rates of a Restored Prairie and a Conventional Corn/Soybean Rotation.

Abstract

Abstract With our changing climate and growing population, it is important to reduce atmospheric carbon. A proposed strategy to reduce atmospheric carbon is the restoration of native prairies, thus converting croplands to prairies (grasslands). Using eddy covariance measurements, we investigated the carbon and water balance of two managed ecosystems over a 4-year period: A restored prairie and a conventional corn/soybean rotation system (cropland) that is tilled annually, at the University of Minnesota Rosemount Research and Outreach Center. The restored prairie is managed with a controlled burn every four years. Over the 4-year period, while the conventional corn/soybean rotation system had a somewhat greater Gross Primary Productivity (GPP) and also respired more carbon, the restored prairie had a much greater net gain of carbon (Net Biome Productivity; NBP); where the prairie experienced a net gain of 1127 +/- 30gC/m2 and the cropland had a net loss of 279 +/- 94gC/m2. The reason for this is that the carbon loss via burning from the prairie was much smaller (approximately 355gC/m2) than the carbon “lost” from harvesting the grain (1172gC/m2). The conventional corn/soybean system had a greater cumulative evapotranspiration (ET) of 2112mm, while the Restored Prairie had a corresponding ET of 1772mm over the entire study period. The water-use efficiency (WUE) for both ecosystems were 0.84 g C mm-1 and 0.42 g C mm-1 for the prairie and cropland respectively. We find that prairie restoration is an effective measure to help reduce atmospheric carbon and reduce water use.