funding: DOE BER Office of Science DE-FC02-07ER64494 funding: DOE BER Office of Science KP1601050 funding: DOE EERE OBP 20469-19145 funding: NNH08ZDA001N funding: NNH12AU03I funding: CSREES-2009-34263-19774 (G-1449-1) funding: NIFA-2010-34263-21075 (G-1470-3)