Emma Bricchi

The influence of air temperature on the starting dates of the pollen season of alnus and populus

Abstract In this work we have studied the influence of air temperature on the starting dates of Alnus and Populus pollination in two different climatic regions in Europe: central Italy and The Netherlands. The start of the Alnus pollen season varied between 27th January and 16th February in the Italian stations while in The Netherlands it showed an average delay of about one month. For Populus the beginning of the pollen season was delayed on an average 15 days at Dutch places compared to central Italy. In the former it varied between 14th March and 21st April while in the latter between 28th February and 24th March. Significant correlations exist between the beginning of pollination for these taxa and temperature conditions in the preceding periods. The highest correlations found were with daily mean decade temperature for three decades before the average starting dates of the pollen season. These correlations were better for The Netherlands than for central Italy perhaps because the temperature in Holla...

A predictive study on the beginning of the pollen season for Gramineae andolea europaea L.

SummaryOn the basis of the results of seven years (1982–1988) of pollen and meteorological monitoring in the atmosphere of Perugia and Ascoli Piceno (central Italy) beginning of pollen season forecasts for Gramineae and Olea europaea L. are reported. The beginning of the pollen season for grass varied between May 2 nd and May 27th while for Olea it varied between May 26 th and June 23rd. By a statistical analysis of these data several significant correlations were found between the onset of the principal period of pollination and the air temperature in the preceding months and the number of «heat units» required to flower. Utilizing multiple regressions a predictive method of the beginning of pollen season for both the taxa is reported.

Comparative study of airborne pollen concentrations in central Italy and the Netherlands (1982–1985)

Abstract Airborne pollen concentrations, measured continuously with a volumetric method at two places in central Italy and in The Netherlands, are compared with respect to both their quantitative and seasonal aspects. Special attention was given to three taxa which occur in the two geographically distinct regions and are known to cause allergic sensitization: Alnus (alder), Poaceae (wild grasses), and Artemisia (mugwort). Averagely, total pollen concentrations are slightly higher in central Italy. The start and the main period in early spring of the season of Alnus pollen, which is more common in The Netherlands, is rather variable from year to year, in both regions correlated with the air temperature in the preceding months. Poaceae pollen, making up to 10 to 20% of the total annual pollen concentrations in both regions, has its start and main season in late spring about one month earlier in central Italy than in The Netherlands, strongly correlated with air temperatures in April and May. The main period...

The use of the pheno-climatic model for forecasting the pollination of some arboreal taxa

Air temperature is one of the most frequent parameters for the application of pheno-climatic models which can give information for the forecasting of the beginning of pollination of various species. For the present study 12 years of aerobiological monitoring data concerning the pollination of hazel, alder, elm, poplar, and willow have been employed to forecast the beginning of their pollination assuming that the beginning of pollination of one species corresponds to a specific moment of phenological development for another species with later pollination. The difference expressed in days between the pollination of two winter taxa with successive flowering is very variable. If this interval is expressed in terms of heat (summation of mean daily temperature above a certain threshold) the differences are smaller. The delay between the pollination of alder and elm varies between 3 and 21 days depending on the climatic trend, but during this period elm on average accumulates 26 degree-days (base temperature 4°C) with a lesser variability. In this way we can begin to calculate the heat requirement for elm from the beginning of alder flowering. This application can be used for other couples obtaining statistical values which are more significant than those obtained with the phenological model, with the exception of willow. The results indicate that for the majority of the species with winter flowering there is a linear relation between the flowering dates and air temperature.

The role of air temperature in determining dormancy release and flowering ofCorylus avellana L.

Summary7 years of airborne pollen monitoring in Perugia (central Italy) were used to determine the temperature requirements to break dormancy and to resume growth and bloom ofCorylus avellana L.,Corylus needs 1000 chill-units to complete its dormancy and this value, in the Perugian area, is met by the end of December or the first days of January. MoreoverCorylus trees require 220 growth degree hours before they are able to flower. If air temperature is high, this value can be achieved in only 10 days, but if the temperature remains too low, the heat accumulation can require up to 35 days. With these parameters it is possible to build a model to predict the date of the beginning ofCorylus avellana pollen season.

Experimental results about Platanus pollen deposition

A comparison between the aerobiological and floristic data carried out for Platanus are reported. The source was constituted by 60 Platanus trees. When they were pollinating we calculated the total pollen prodution of the source, controlling the number of male inflorescences for each plant, the number of anthers for each inflorescence and the number of pollen for each anther. Aerobiological data were obtained with 16 Durham gravimetric samplers positioned over an area of approximately 25 km2 at variable distances and in different directions to capture pollen transported by winds coming from any direction.In the first year of analysis, we carried out two kind of aerobiological monitoring positioning a Hirst volumetric trap near the closest gravimetric sampler. The two methods showed a similar trend in Platanus pollen profiles. In the following years, only Durham gravimetric samplers were used to study pollen dispersion. The data showed that there were high concentrations of pollen on the soil near the source while at distances higher than 800 m pollen concentration decreased dramatically. About 1/4 of all the pollen produced fell in an area within 400 m from the source and at a distance of 2750 m only 9 pollen grains/cm2 fell throughout the entire season.

Airborne pollen content in the atmosphere of central Italy (1982–1986)

This report describes qualitatively and quantitatively the content of pollen in the atmosphere of central Italy during the five years 1982–1986. Total production in this period showed fluctuations depending on the flowering seasons of the anemophilous taxa. The season of maximum pollen concentration was from April to July, with a prevalence of arboreal pollen in thefirst months, and of pollen from herbaceous plants in the last months of the year. During the five years of research more than 81 different types of pollen grains were recorded and identified. In both the cities investigated Curpessaceae/Taxaceae, Fagaceae, Oleaceae Gramineae and Urticaceae were responsible for the greatest amounts of pollen.

Time linkages between pollination onsets of different taxa over an 11-year period in Perugia, Central Italy

Times of pollination of different taxa in the atmosphere of Perugia (Central Italy) over an 11-year period (1982–1992) were recorded and analysed by means of a 7-day volumetric Hirst-type pollen trap. For some taxa, the pollination period varied from year to year from a chronological and/or quantitative point of view. Several taxa showed a linkage in their starting dates of pollination. Knowledge of this kind of linkage allows us to build a forecasting model.

Airborne pine (Pinus spp.) pollen in the atmosphere of Perugia (Central Italy): Behaviour of pollination in the two last decades

The phenology of many species, which grow intemperate climate, is principally regulated bythe temperature and the plants respond withvariations in the beginning, in the durationand in the intensity of the various phenophasestowards every climate change. We have analysedthe data of Pinus pollination in Perugia,Central Italy, during last 2 decades(1982–2001), in a period during which theannual mean temperature significantly increasedby about 0.8 °C.The pine pollination started, on average,between the end of March and mid-April andended in the last days of June, with a meanduration of 65 days. The start dates showed asignificant negative correlation with theaverage air temperature in March andsignificant trends towards an earlier beginningof pollination by 18 days (−0.9 day/year) and ashorter duration of the pollen season by 10days (−0.6 day/year) were found over thestudied period. Moreover, the trend of thedaily pollen counts showed, on average, analmost normal distribution, but the analysis ofeach yearly trend revealed significantdifferences correlated with the meantemperature during the pollen season. Theseobserved trends in pine pollination suggest theuse of aerobiological monitoring of thisairborne pollen as indicator of temperaturechange in Central Italy over a relatively longperiod.

Daily variations of Urticaceae pollen count and influence of meteoclimatic parameters in East Perugia during 1989

SummaryUrticaceae pollen monitoring was carried out, in the atmosphere of East Perugia during the summer of 1989. In summer the Urticaceae pollen shows a fluctuating diurnal trend, which was analysed daily over six 4-hour periods. The high peaks of thistaxon were recorded in the middle of the day in July and August, and in the morning in June. The percentage pattern of the daily mean pollen concentration of Urticaceae was compared with mean temperature, wind speed, relative humidity and rain, both in the non-rainy days and rainy ones. The best correlations came out comparing pollen concentration and meteoclimatic parameters during non-rainy days. The interpretation of the influence of rainfalls is very difficult owing to their peculiar features in summer.