Airborne pollen reflects local vegetative composition and is a proxy for flowering phase. Long-term pollen data might reflect changes in biodiversity and phenology, attributable also to the effect of climate change. The present study, based on pollen data collected within the Italian aerobiological network POLLnet , aimed to verify whether there is any evidence of temporal changes in pollen season timing and its relation with meteorological variables. To this purpose, nine stations located in North and Central Italy were selected, and twelve pollen taxa, both arboreal and herbaceous, were considered. For each taxon and station, 11–17-year datasets of airborne pollen concentration within the period 2000–2016 were analysed. Four different pollen season descriptors were elaborated (start, end and peak date, season length) and analysed their temporal trend, also in relation to temperature and precipitation. Overall, the results showed a negative temporal trend in pollen season starting date, which indicates a tendency towards an earlier flowering for Corylus , Quercus , Gramineae and Urticaceae in all stations (even if statistically significant in six out of 36 cases). The effect of meteorological parameters was evidenced by negative correlations between pollen season starting date and temperature. With the exception of Olea , Ambrosia and Artemisia , all the remaining pollen taxa showed significant (negative) correlations between pollen season start date and average temperature of the previous months in at least half of the stations. As for precipitation, no relevant correlations were detected with pollen season parameters. The results are also interpreted considering the different biogeographic areas in which the nine stations are located. Long-term pollen dataset is useful in phenological studies and for the detection of climate change effects.

中文翻译：

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空气中花粉季节性的时间趋势：来自意大利 POLLnet 网络数据的证据

空气中的花粉反映了当地的植物成分，是开花期的代表。长期花粉数据可能反映生物多样性和物候的变化，也可归因于气候变化的影响。本研究基于意大利空气生物网络 POLLnet 收集的花粉数据，旨在验证是否有任何证据表明花粉季节时间的时间变化及其与气象变量的关系。为此，选择了位于意大利北部和中部的九个站点，并考虑了十二个花粉类群，包括树栖和草本植物。对于每个分类群和站点，分析了 2000-2016 年期间 11-17 年的空气传播花粉浓度数据集。详细阐述了四种不同的花粉季节描述符（开始、结束和高峰日期、季节长度）并分析它们的时间趋势，也与温度和降水有关。总体而言，结果显示花粉季节开始日期的时间趋势为负，这表明所有站点的 Corylus 、 Quercus 、 Gramineae 和 Urticaceae 都有更早开花的趋势（即使在 36 个案例中有 6 个具有统计意义）。花粉季节开始日期和温度之间的负相关证明了气象参数的影响。除了油橄榄、龙涎香和蒿外，所有剩余的花粉类群在至少一半的站点中都显示出花粉季节开始日期与前几个月平均温度之间的显着（负）相关性。至于降水，没有检测到与花粉季节参数的相关性。还考虑了九个站点所在的不同生物地理区域来解释结果。长期花粉数据集可用于物候研究和检测气候变化影响。