Modelling the pollen season start in Corylus avellana and Alnus glutinosa

Abstract

Hazel (Corylus avellana L.) and black alder (Alnus glutinosa (L.) Gaertn.) are important sources of airborne pollen and represent an allergen threat during the flowering period. Researches on airborne pollen concentrations in both species are useful in allergology, as well as for fruit production for hazel. The aims of the present study were: (1) to investigate the relationships between environmental conditions and the airborne pollen concentration of hazel and black alder during the flowering period by correlation and multiple regression analysis and (2) to predict the pollen season start (PSS) by using a sequential model, in order to obtain a helpful tool in allergology and hazel cultivation. In this study, the applied method defines the pollen season as the period in which 90 % of the total season's catch occurred, using a data set of 18 years (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014). The relationships between daily meteorological parameters (temperature, humidity, rainfall and wind speed) during the 14-day period that precedes the PSS and the PSS of hazel and black alder (day of the year) were investigated. The results showed that mean temperature and the number of rainy days before the PSS are the main factors influencing PSS for both taxa. Moreover, the chilling and heat needed to break dormancy were estimated in order to predict the PSS of both species. Different years and different thresholds of temperature and chill days were used to calibrate and validate the model. Keywords Black alder _ Chilling units _ Hazel _ Pollen season start _ Sequential models

The effects of climate change on the flowering phenology of alder trees in southwestern Europe

“…Previous studies have noticed the importance of chilling accumulation for alder and other winterflowering trees in the last autumn. The chilling phase has been identified as the most important thermal accumulation period for alder in the Mediterranean climate while forcing requirements are satisfied in a short period of time in alder trees of Southern Europe (González-Parrado et al, 2006;Novara et al, 2016). It supports the results of our study, but such behavior with respect to the thermal requirements may be different in other climatic conditions.…”

“…autumn temperatures have become warmer during recent years. Similar phenological trends were found in other Mediterranean areas of Southern Europe, such as Italy and the Iberian Peninsula, where a slight trend towards later start-dates of alder pollen seasons has been documented (Jato et al, 2013;Novara et al, 2016;Rodríguez-Rajo et al, 2011). On the other hand, these results contrasted with those from Central and Northwestern Europe (United Kingdom, Austria, Finland, Norway, Sweden, Iceland) (Emberlin et al, 2006;Jäger et al, 1996;Lind et al, 2016;Smith et al, 2014), all of which reported negative trends, i.e., alder flowering earlier over time.…”

Comparative long-term trend analysis of daily weather conditions with daily pollen concentrations in Brussels, Belgium

“…The release from winter dormancy is environmentally mediated by species-specific responses to temperature and photoperiod. The “chilling and heating” mechanism is similarly described for the flowering phase and pollen release, especially for alder and hazel in early year, and so has been used for the development of pollen forecast models (Novara et al 2016 ). However, our study does not take into account the chill accumulation during the previous winter period.…”

“…However, these consequences may significantly vary from one region to another, depending on the selected taxon and on the clime (Donders et al 2014 ; Emberlin et al 2002 ; Galán et al 2005 ). Indeed, the complexity of interactions and overlapping actions between meteorological parameters, the plant physiognomy and phenology, the land use, and other environmental factors presents a serious challenge for researchers to develop robust and precise pollen forecast models (Novara et al 2016 ; Sofiev et al 2015 ). Pollen monitoring thus plays a crucial role to improve these models by feeding them with historical data.…”

Viability and germinability in long term storage of Corylus avellana pollen

“…For this reason, hazel requires genetically compatible pollinizer cultivar, but pollination remains an uncertain process dependent on numerous factors, such as rainfall, humidity, wind, which can affect this phenomenon in different ways (Ellena et al, 2014;Novara et al, 2016) both during the catkins elongation and pollen dispersion. Moreover, male and female flowering of compatible cultivars should overlap in order to ensure a correct pollination, but flowering can vary from year to year and the response of male anď et al, 2012; Ellena et al, 2014).…”