Title: Quantifying targets to manage invasion risk: light gradients dominate the early regeneration niche of naturalized and pre-commercial Miscanthus populations Authors
Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2014
Publication Date: N/A
Interpretive Summary: Pressure to produce ever-increasing amounts of biomass for bioenergy production has led to the introduction and deployment of a variety of novel high-yielding bioenergy crops to U.S. cropping systems. The rapid growth, resilience and capacity for spread of many of these crops increases the likelihood that unwanted, invasive escapes from production systems into natural ecosystems will occur. Limiting invasive spread of bioenergy crop escapes depends on a three-stage management approach: 1) prevent escapes through careful selection of bioenergy crop cultivars; 2) use best management practices, including selection of flat, low-disturbance sites well-away from waterways and surrounding fields with mowed buffer areas, among others; and 3) monitor surrounding areas that are likely to serve as early establishment sites for crop escapes and eradicate detected populations. This study focuses on the last of these practices, using a greenhouse study to quantify the environmental conditions (including light, soil moisture and plant residue cover of the soil surface) promoting establishment of seeds of a pre-commercial Miscanthus giganteus bioenergy cultivar and a known invasive genotype of Miscanthus sinensis. We found that light was the most important factor for establishment success, although Miscanthus seedlings could germinate and remain in a suppressed state under all but the lowest light levels. These results indicate that high-light environments in potential receptor areas, such as abandoned agricultural fields or canopy gaps in forests, are likely to be the highest priority targets for monitoring of escapes surrounding Miscanthus production fields.
Technical Abstract: Prospective bioenergy crops have caused concern about their invasive potential because they often share characteristics with known invasive species. Studies that examine the factors that limit regeneration of these crop species will be crucial for identifying vulnerable habitats and devising management strategies to reduce the likelihood of escape from cultivation. Using a response surface design, we investigated the influence of light availability, soil moisture, and litter cover on recruitment and establishment of a potential biofuel cultivar of Miscanthus as well as an invasive congener. Responses were similar for the two plant types. Light availability had a strong influence on seedling success at both stages, though light limitation prevented establishment only at the lowest light level. Though variation in recruitment rates was low within plant types, establishment varied extensively in response to different light conditions. Low variation in Miscanthus seedling recruitment that led to establishment of a seedling bank under a range of light intensities may facilitate a “sit and wait” situation that raises the likelihood of successful escapes. Therefore, management efforts that restrict seed movement and increase light competition for seedlings will be important for lowering invasion risk. As deliberate introductions of bioenergy crops increase, ecological studies that quantify conditions required for successful escapes will be key to helping agronomists and managers mitigate the risk of unintended invasions.