Abstract
The possibility of increased invasiveness in cultivated varieties of native perennial species is a question of interest in biofuel risk assessment. Competitive success is a key factor in the fitness and invasive potential of perennial plants, and thus the large-scale release of high-yielding biomass cultivars warrants empirical comparisons with local conspecifics in the presence of competitors. We evaluated the performance of non-local cultivars and local wild biotypes of the tallgrass species Panicum virgatum L. (switchgrass) in competition experiments during two growing seasons in Ohio and Iowa. At each location, we measured growth and reproductive traits (plant height, tiller number, flowering time, aboveground biomass, and seed production) of four non-locally sourced cultivars and two locally collected wild biotypes. Plants were grown in common garden experiments under three types of competition, referred to as none, moderate (with Schizachyrium scoparium), and high (with Bromus inermis). In both states, the two “lowland” cultivars grew taller, flowered later, and produced between 2x and 7.5x more biomass and between 3x and 34x more seeds per plant than local wild biotypes, while the other two cultivars were comparable to wild biotypes in these traits. Competition did not affect relative differences among biotypes, with the exception of shoot number, which was more similar among biotypes under high competition. Insights into functional differences between cultivars and wild biotypes are crucial for developing biomass crops while mitigating the potential for invasiveness. Here, two of the four cultivars generally performed better than wild biotypes, indicating that these biotypes may pose more of a risk in terms of their ability to establish vigorous feral populations in new regions outside of their area of origin. Our results support an ongoing assessment of switchgrass cultivars developed for large-scale planting for biofuels.
Highlights
The once extensive North American tallgrass prairie exists mostly as small, isolated remnant prairies scattered throughout the historical range [1]
Efforts to improve biodiversity and ecosystem function of the tallgrass prairie expanded the use of native grass cultivars for restoration and conservation projects. One example of such widespread cultivar use is in the Conservation Reserve Program (CRP), a land conservation effort managed by the U.S Farm Service Agency in which agricultural land is planted with grassland vegetation to improve soil and water quality and provide wildlife habitat [3]
We hypothesized that non-local cultivars with enhanced growth traits would outperform local wild biotypes under competitive conditions in these experiments
Summary
The once extensive North American tallgrass prairie exists mostly as small, isolated remnant prairies scattered throughout the historical range [1]. In the US, organized efforts in prairie grass cultivation began in the 1930s, following the Dust Bowl. Traditional cultivars were planted for forage and for soil and water conservation [2]. Efforts to improve biodiversity and ecosystem function of the tallgrass prairie expanded the use of native grass cultivars for restoration and conservation projects. One example of such widespread cultivar use is in the Conservation Reserve Program (CRP), a land conservation effort managed by the U.S Farm Service Agency in which agricultural land is planted with grassland vegetation to improve soil and water quality and provide wildlife habitat [3]
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