Ambrosia L. in Catalonia (NE Spain): expansion and aerobiology of a new bioinvader

This paper aims to determine the stage of the naturalization of ragweed (Ambrosia L.) in Catalonia, north-east Spain, and to analyze the airborne pollen pattern and provenance, in order to contribute to a better management of it and prevent the expansion of a possible new bioinvader that can also become a health problem due to its highly allergenic pollen. Biogeographical sampling consisted on the monitoring of Ambrosia populations through the territory over a 2-year period (2010-2011). Aerobiological sampling was based on the analysis of pollen records at eight aerobiological sampling stations, during the period 1994-2010. Pollen provenance sampling was examined using backward atmospheric air masses trajectories and synoptic maps, as well as through the application of a source-receptor model. Ambrosia colonies are expanding throughout the territory at a mean growing rate of 324% for the sampled territory. The Annual Pollen Indices appear to be clearly influenced by the pollen concentrations in the peak dates, and these are linked to long-range transport of pollen from regions where Ambrosia is widely widespread, such as eastern France, northern Italy and Hungary and Serbia. The episodes of pollen transport are increasing in number. Although airborne Ambrosia pollen type is not showing any clear increasing trend for the period under study, local populations of the plant could be having an influence on the pollen records, since the genus is clearly expanding in the territory at considerably high spread rates. Ambrosia populations have to be surveyed both for public health reasons and as a new bioinvader.