Background/Question/Methods:
In an effort to reduce greenhouse gas emissions, expand domestic energy production, and maintain economic growth, public and private investments are being used to pursue dedicated feedstock crops for biofuel production.  The leading candidate for lignocellulosic-based ethanol in the US is switchgrass (Panicum virgatum), a perennial rhizomatous grass native to most of North America east of the Rocky Mountains.  Switchgrass possesses great genetic variation, harbors few resident pests, and is highly productive in marginal environments – all traits conducive for biofuel production.  However, the same traits that are agronomically favorable also create the potential for switchgrass to escape the cultivated environment and become an invasive species.  Commercial switchgrass production is being proposed in the non-native region of the Pacific Northwest and California, which are environmentally dissimilar to most regions of its native range.  California’s Mediterranean climate receives much lower precipitation amounts and in different seasons compared to the native range of switchgrass.  Additionally, California has thousands of miles of irrigation canals and many thousand acres under paddy rice production, both of which possess anoxic soils.  Switchgrass has both upland and lowland ecotypes, which are adapted to mesic and hydric soils respectively, and may differ in their ability to survive in California.
            To assess the ability of switchgrass to survive outside cultivation in the unique California environment where it is non-native, we conducted a soil moisture stress experiment with four cultivars, two from both the upland and lowland switchgrass ecotypes.  This experiment maintained switchgrass individuals under no stress, chronic drought stress, and chronic anoxic soil stress via flooding.
Results/Conclusions
All cultivars survived ten weeks under both drought (~5% soil moisture) and flooded (~60% soil moisture) conditions. Lowland forms were equally productive (i.e., tiller production) under flooded and control conditions, while across ecotypes, control plants produced greater the two-fold more tillers and were 20% taller than drought individuals.  Sexual reproduction was unaffected by soil moisture treatments.  However, across all treatments, upland individuals were twice as likely to flower compared to lowland individuals.  Switchgrass appears to be highly tolerant of extremely low soil moisture and flooding conditions, suggesting that both arid and hydric sites will support a switchgrass population without human cultivation. Programs aimed at enhancing the already tolerant switchgrass cultivars to xeric soils will further increase the ability of switchgrass to become an invasive pest.