Abstract
The application of phenological data together with meteorological and pollen data in a comprehensive analysis gives an opportunity to draw conclusions on variability of the starting date of the pollen season and its dynamics in terms of meteorological factors. It is quite important especially due to the fact that studies conducted all over Europe have proved that species phenology responds to climate warming trends. There has been observed a tendency to an earlier onset of spring flowering and leafing as well as the lengthening of the growing season. Although phenological network studies differ with regard to regions, species, events observed and applied methods, their data show a clear temperature-driven extension of the growing season by up to 2 weeks in the second half of the 20th century in mid- and high northern latitudes; for example, in Germany changes in timing of phenological spring events have been estimated at about -1.6 days / decade, while in Switzerland: -2.3 days / decade. Despite interannual variability in flowering date, caused by specific meteorological conditions each year, long-time series of phenological data from the area of Poland have proved that hazel flowering occurred in the surroundings of Warsaw later in the 50's (third decade of March) than it is observed at the beginning of the 21st century (second decade of March). There is a lack of such long time series of pollen data, but we can suspect that the hazel pollen season has changed similarly to the time pattern of its flowering. Plants are very sensitive to weather conditions, therefore it is important to know as precisely as possible the impact of meteorological conditions on a plant's reactions. The determination of thermal thresholds for a specific plant's reactions may be beneficial for this purpose. The estimated value of Positive Degree Days (PDD> 50), which caused the first <i>Corylus</i> flowers (F2 phenophase) to bloom in the study years, requires testing in future years to make the threshold values credible.
Highlights
Phenology is a study of the timing of recurring biological events in the animal and plant world
The pollen season was defined as the period when 95% of annual total pollen grains appeared in the air
Phenology data were taken from the Institute of Meteorology and Water Management database that contains information on the generative development of plants, observed using Łukasiewicz’s method in 7 stages: F1 – the appearance of the first flower or inflorescence buds; F2 – first bloom; F3 – beginning of full bloom (25% of flowers open); F4 – the first flowers shedding blossom; F5 – end of full bloom (75% of flowers shedding blossom); F6 – the last flower buds; F7 – end of flowering
Summary
Phenology is a study of the timing of recurring biological events in the animal and plant world. The pattern of plant phenophases is an expression of thermal effects, changes in sunlight, and humidity conditions. The seasonality of vegetation is manifested by the presence of pollen grains in the air. Values are characterized by great instability (Walanus , 1994). They depend on many different factors, such as the proportion of a given taxon in the vegetation, long-distance transport, and meteorological conditions (Pidek , 2007). Numerous analyses have demonstrated that pollen concentration is correlated significantly with different meteorological parameters, such as maximum air temperature, maximum wind speed, and humidity (Pidek , 2007; P u c , 2007)
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