Evaluation of factors influencing the eradication of annual bluegrass (Poa annua L.) from Point Thomas Oasis, King George Island, Maritime Antarctica.
From 2014 to 2018, we performed three on-site eradication actions of Poa annua occurring on King George Island. We aimed at (1) assessing the population response to eradication efforts, (2) evaluating the campaign success, and (3) identifying the most important factors likely to influence eradication success. The first partial eradication action reduced the initial population of around 1500 tussocks to around 1100 tussocks with less than 4 m2 canopy area. In treated locations, we observed high re-establishment where no soil removal was performed, while only a marginal recruitment where plants were removed with associated soil. In the 2017/2018 season, we recorded over 1800 tussocks, which all were subsequently removed. Performing eradication according to the prescribed scheme (plant and soil removal) should result in eradication success. We evaluate that the probability of successful eradication of the population is high because of small size and number of separate infestation sites, complete spatial and ecological isolation of infestation, high accessibility of target population, and well-known current location of infestation sites. The factors which reduce the likelihood of eradication success are long reaction time, high adaptation of the species to new environmental conditions, and high propagule longevity. Reinvasion possibility and frequent personnel changes in the eradication team resulting in varying levels of personnel awareness and experience may also negatively influence eradication success. An invasion, not managed for many years, may still be targeted, but its successful eradication depends on the "human factor", which may drive the success of the action in opposing directions.