Abstract
A significant increase in summer temperatures has been observed for the period 1996–2011 in Poznań, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Poznań by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann–Kendall test and Sen’s slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman’s rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July–September daily minimum temperatures (r = −0.644, p < 0.01). In contrast, no significant correlations were found between temperature and characteristics of Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Poznań, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.
Highlights
Climate change is generally characterised by the increasing trends of average annual surface temperature, which in Europe exceeded 0.9 °C for the period 1901–2005 (Solomon et al 2007)
All detected series were characterised by a significant temperature increase and the most distinct one was observed during the July–September period (+0.16 °C/year, p
It is worth noticing that Artemisia pollen season start dates significantly correlated with mean daily minimum temperatures in July (r=−0.805, p
Summary
Climate change is generally characterised by the increasing trends of average annual surface temperature, which in Europe exceeded 0.9 °C for the period 1901–2005 (Solomon et al 2007). Temperature increase is closely related to the longer growing season and advance of flowering time of plants (Walther et al 2002). Some of these plants are of a great economic, ecological and health importance, and so it is essential to quantify any influence of climate variability on their phenophases (stage in a plant’s life cycle), such as budburst, fructification and flowering (Peñuelas and Filella 2001)
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