The Italian Network POLLnet: the database as background to detect airborne pollen trends and investigate climate change effects

Airborne pollen reflects structure and changes in vegetation .It is well known that pollen seasons and their intensity could help to detect the effects of climatic changes so pollen is a good bioindicator. Our investigation has been supported by a national network among regional agencies; each centre refers to the same protocol compliant with UNI 11108 subsequent amendments . Thus, it was possible to obtain reliable data, consistent with accuracy and precision requirements. Aim of this work is to draw attention on possible trends in the parameters describing the pollen season and pollen amount and to investigate the role of meteorological factors. Aerobiological data were validated; comprehensiveness requirements of the data set were established. Nine different pollen descriptors were considered and examined in relation with different meteorological parameters through a non parametric statistical approach. We took into account 9 stations in northern and central Italy, analysing 12 herbaceous and arboreal taxa during a time period from 2000 to 2017. The first results show a homogeneity of trends of the pollen season’s indicators. Trends of general advance in the starting date for Poaceae, Urticaceae, Quercus and Corylus and in the peak date for Poaceae and Corylus is one of the most relevant signals found. On the other hand, trends related to indicators of pollen production (peak value and pollen index), which are certainly more influenced by local features, are less homogeneous. The effects of climate change are underlined by several relevant signals of (negative) correlation with temperature. For some taxa it is possible to highlight a relevant connection both with minimum temperature (with particular reference to the winter and autumn one) and with the maximum (winter and spring) temperature; as regards precipitations, relevant values of correlation appear only occasionally. Conclusions: The obtained results are reported and discussed in light of the state of the art.