CONFERENCETrends in aerobiological and phenological processes of birch in Latvia 2003-2014
Olga Ritenberga
University of Latvia, Faculty of Geography and Earth Sciences
Gunta Kalvane
University of Latvia, Faculty of Geography and Earth Sciences
DOI: 10.22364/fg.15.12
Keywords: birch flowering, birch pollen season, seasonal pollen index, Latvia
Abstract
Changes in the start dates of pollen seasons and the birch flowering times depend on increasing of daily mean air temperature. Birch flowering usually starts on the third decade of April, three weeks later then the start of pollen season, due to long-range pollen transport by air currents. Extremely large SPIs were detected in the years 2012 and 2014 in comparison with previous 12-year period of observations. Phenophase trends were found to be negative; the phase onset (birch leaf unfolding and flowering) is earlier at the end of considered period. The trends of the onset of birch sap circulation are neutral, however the year-to-year variation is high.