Native Perennial Grassland Species for Bioenergy: Establishment and Biomass Productivity

Published in Agron. J. 103:509–519 (2011) Published online 7 Feb 2011 doi:10.2134/agronj2010.0360 Copyright © 2011 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. I worldwide demand for energy and the growing concern over global climate change have led to a surge in renewable energy research. Th is research encompasses a wide variety of initiatives aimed at fi nding reliable, sustainable, domestic fuel sources that reduce dependence on fossil fuels and minimize greenhouse gas emissions and other negative environmental impacts. Th e Energy Independence and Security Act of 2007 (EISA) requires 136 billion L of renewable transportation fuels be available in the United States by 2022, and 60 billion L will be from advanced cellulosic sources. Achieving these goals will require the development of reliable large-scale production of diverse energy feed stocks. Th e development of corn (Zea mays L.) grain ethanol brought renewable energy into the public arena and raised awareness about the potential for development of domestic energy sources (Solomon et al., 2007). However, growing concern over the environmental impact and economic viability of corn grain ethanol has prompted many to advocate for “second generation” bio-energy crops (Sanderson and Adler, 2008; Sarath et al., 2008). Th e most extensively studied of these crops are switchgrass (Panicum virgatum L.), reed canarygrass (Phalaris arundinacea L.), miscanthus x giganteus (L.), and alfalfa (Medicago sativa L.) (Sanderson and Adler, 2008). Th e cellulose, hemicellulose, and lignin components of these crops can be converted to energy-rich gases or liquid fuels and used to generate electricity or synthesize transportation fuels (Downing et al., 1995; McLaughlin et al., 2002; Parrish and Fike, 2005). While many herbaceous and woody crops are being considered as next generation biofuels, perennial grasses have received the most research attention (McLaughlin and Walsh, 1998). Perennial grasses, specifi cally switchgrass, have high biomass yield potential, can be cultivated on agricultural or marginal land, and are oft en associated with ecological services (McLaughlin and Walsh, 1998; Parrish and Fike, 2005). Compared to annual crops like corn, perennial grasses can reduce soil erosion (McLaughlin and Walsh, 1998), provide greater nutrient capture and utilization, increase carbon storage and soil organic matter (Frank et al., 2004), and reduce loss of soil nutrients and improve soil fertility (McLaughlin and Kszos, 2004; Sanderson and Adler, 2008; Tilman et al., 2006). While perennial grasses show great potential as bioenergy crops (Casler et al., 2007; Lee and Boe, 2005), there is debate about how they should be cultivated to maximize both biomass yield and ecological benefi ts. Proposed perennial bioenergy cropping systems include grass monocultures (Adler et al., 2006; Lee and Boe, 2005; Lemus et al., 2002), low diversity polycultures (Picasso et al., 2008; Tracy and Sanderson, 2004), or high diversity polycultures (Tilman et al., 2006). Th ese cropping systems include a range of species diversity and require diff erent management strategies. Th e greatest distinction between these cropping systems is the proposed level of species richness and desired botanical composition. Ecologists have traditionally advocated for high diversity mixtures for biodiversity conservation while agronomists have advocated for low diversity mixtures or monocultures to maximize biomass yield (Picasso et al., 2008; Russelle et al., 2006). According to Tilman et al. (2006), polycultures of native grasses, legumes, and forbs ABSTRACT