Disturbance and nutrient availability drive absinthe (Artemisia absinthium) invasion in a native rough fescue grassland

Understanding plant invasion is a critical issue in the conservation of native grasslands. Diverse and productive plant communities may inhibit invader establishment via biotic resistance, whereas disturbances may facilitate invasion by weakening resistance. These factors may also interact, yet their combined effects on invasion are unclear. Absinthe (Artemisia absinthium) is an invasive herbaceous species of North American grasslands that can impact biodiversity and forage production, yet little is known about its invasion ecology. To fill this gap, we established an experiment manipulating disturbance via herbicide and fire, as well as resources via fertilizer addition, to explore mechanisms of absinthe invasion into native grassland. We transplanted absinthe seedlings into treated plots, then measured survival and growth along with changes in the plant community. Absinthe survival was approximately 65%, except in undisturbed plots with added fertilizer where it was reduced by 50%. High survival also corresponded with the abundance of other invaders suggesting potential facilitation among invaders. Absinthe growth, conversely, was higher in disturbed plots especially when fertilizer was added. Combined, these results indicate that productive communities may have greater biotic resistance to absinthe invasion but that, when disturbed, these communities are at the greatest risk.