Present and past pollen rain: aerobiological data applied to palaeoenvironmental reconstructions

Links between the different fields of palynology gave extremely interesting insight to solve problems of pollen representation in past and present contexts. For example, there is general consensus on the importance of application of archaeopalynological techniques to forensic sciences, or on the studies of modern pollen rain for inferring the Relevant Source Area useful for past land-use reconstructions. The application of aerobiological studies to past palaeoenvironmental reconstructions is, therefore, a further very interesting field of investigation that, though not still completely explored, may be vector of new important inferences about past, present and future of climate change. Data of airborne pollen of Castanea and Taxus from aerobiological monitoring are presented as examples of studies on taxa of great interest for the development of plant landscape in Italy. Airborne pollen was monitored through continuous sampling with a Hirst volumetric sampler for 18-years. As for Castanea, long-distance transport of this pollen is well-known, but studies on modern pollen rain show that a relatively small amount of pollen is compatible with the presence of chestnut trees in the area. As for Taxus, pollen production has decreased, while total woody pollen abundance in air has increased in the time period studied. The trend of the Taxus pollen season shows a delay at the beginning, a shortening of the pollen period, and an advance of the end of the pollen season. This was interpreted as a response to climate warming. In particular, Taxus follows the behaviour of winter-flowering plants, and therefore earlier pollination is favoured at low autumn temperatures, while late pollination occurs more often, most likely after warm autumn temperatures.