Miscanthus × giganteus, a widely planted biofeedstock, is generally regarded as a relatively low invasion concern. As a seed-infertile species, it lacks a consistent mechanism of long-distance dispersal, a key contributor to invasion rate, and constitutes a low risk for cultivation escape. However, agricultural production shelters plants from stochasticity and increases propagule pressure, enhancing the potential for low-risk species to take advantage of rare dispersal opportunities. Weed risk assessments of M. × giganteus assume the rarity of events such as scouring and flooding that would facilitate secondary dispersal of vegetative rhizome fragments and the long-term sexual inviability of escapes. Combining data from small-scale rhizome fragmentation and movement experiments, and estimates from the literature, we parameterized an individual-based model to examine M. × giganteus spread given three dispersal scenarios. We further evaluated our estimates in response to different field edge buffer widths and monitoring intensities, two key strategies advised for containing biofuel crops. We found that clonal expansion from the field edge alone was sufficient to allow the crop to outgrow buffers of 3 m or less within 11 to 15 yr with low monitoring intensities. Further, models that included the possibility of rhizome dispersal from fields and scouring at field edges demonstrate the potential for long-distance dispersal and establishment with inadequate management. Our study highlights the importance of considering minimum enforced management guidelines for growers to maintain the ecological integrity of the agricultural landscape.
Nomenclature: Giant Miscanthus, Miscanthus × giganteus J. M. Greef and Deuter ex Hodk. and Renvoize.
Management Implications: Previous assessments of low invasion risk for sterile Miscanthus × giganteus are contingent on the rarity of events that would disperse plant rhizomes from the field edge. Our results demonstrate the importance of implementing monitoring strategies, augmented by field edge buffers that increase detection likelihood, to contain the invasion risk from large-scale cultivation of M. × giganteus. Early detection is key to increasing the success and decreasing the cost of invasive species control. Although opportunities for rhizomes to disperse should be rare, the accumulation of infrequent escapes from large-scale cultivation should be a matter of concern. The combination of field edge buffers and consistent monitoring should form a feasible strategy for containing cultivated plant escapes.