Fig. 2.

The location of pollen-monitoring sites involved in the study, showing the following results calculated using the available number of days when airborne Ambrosia pollen data were recorded during August–September for the years 2004–2013: a the mean number of days when Ambrosia pollen was recorded (maximum 61); b significant trends and the direction of slope of linear regression analysis (only sites with ≥8 years of pollen data). Regions where pollen data were not available are also depicted