Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2012
Publication Date: 4/1/2012
Citation: Matlaga, D.P., Schutte, B., Davis, A.S. 2012. Age-dependent population dynamics of the bioenergy crop Miscanthus x giganteus in Illinois. Journal of Invasive Plant Science and Management. 5:238-248. Interpretive Summary: As demand for alternative fuels continues to grow, biofuels from herbaceous perennial biomass crops will be an important component of the US energy portfolio. Prior to growing such crops across wide areas, it is important to understand both the risks and benefits of such an action. Because of similarities between many bioenergy crops and plant invaders, and new projects to rapidly scale-up biomass production in the Midwest, we felt it important to quantify the invasive potential of a leading candidate for bioenergy production in Illinois, Miscanthus x giganteus (Mxg). We measured Mxg vital rates in plants of varying ages at 13 locations in Illinois to determine the impact of latitude and plant age on growth, survival and reproduction. All M. x. giganteus demographic rates were strongly dependent on plant age. Seed production was low in first year plants, and rose to 170,000 seeds/plant by the fourth year, but none of the seeds were germinable. Vegetative expansion of M. x. giganteus was moderate compared to other large grasses; four year old plants were observed to have a maximum vegetative creep radius of 0.8 m and on average occupy 0.5 m^2. The lack of viable seed production and slow vegetative expansion in M. x giganteus observed in this study suggest that the sterile clonal cultivar for this bioenergy crop has low invasive potential in Illinois.
Technical Abstract: Rising global demand for liquid fuels, coupled with new technologies for converting biomass to ethanol, have generated intense interest in the development of herbaceous perennial bioenergy crops. Some plant species being considered as biofeedstocks share traits with invasive species and have histories of spreading outside of their native ranges, highlighting the importance of evaluating the invasive potential of these species prior to the establishment of large-scale plantings. The Asian grass Miscanthus x giganteus is a candidate biofeedstock for the north central region of the USA. Our goal was to determine the influence of plant age on vital rates and vegetative spread of M. x. giganteus in Illinois. We collected data from 13 M. x. giganteus plantings in Illinois, ranging in age from 1 to 7 years, recording tiller number, plant spatial extent, seed production and survival over 4 years. Additionally, to better understand the recruitment potential of M. x. giganteus we conducted a greenhouse germination experiment and field trials to estimate rhizome fragment establishment. All M. x. giganteus demographic rates were strongly dependent on plant age. First and fourth year Miscanthus x. giganteus plants produced an annual average of over 10,000 and 170,000 seeds/plant, respectively, but none of the seeds were germinable. Vegetative expansion of M. x. giganteus was moderate compared to other large grasses; four year old plants were observed to have a maximum vegetative creep radius of 0.8 m and on average occupy 0.5 m^2. We observed that the density of tillers within the center of a clone decreases likely leading to a ‘dead center’ found among other perennial bunchgrasses. Plant establishment probability increased with rhizome weight, ranging from close to zero for our smallest rhizome fragments to 50% for fragments weighing 20 g. The relationship between age and survival was asymptotic, increasing with age from 30% for first year plants to nearly 100% for four year old plants. The lack of viable seed production and slow vegetative expansion in M. x giganteus observed in this study suggest that the sterile clonal cultivar for this bioenergy crop has low invasive potential in Illinois.