Aerobiology - more than pollen counts? : Poster präsentiert bei: 27. Tagung der Arbeitsgemeinschaft Forstgenetik und Forstpflanzenzüchtung (Walddialog), "Forstgenetik - eine ökologische und ökonomische Zukunft gestalten", Wien, 10. - 13. Oktober 2007
One of the best studied examples fof tbe effects of weather on pollination and seed production is the genus Quercus. Cecich (1999) investigated acorn production within two small oak populations (9 white oak trees - Quercus alba and 12 black oak trees - Quercus velutina) in relation to weather variables like; maximum and average temperature, relative humidity, foggy days, rainly das and days with hail. The Estimated Pollination Date (EPD) for the actual year was calculated 3 days before the pollen was shed, on actual day and 3 days after. The weeks before EPD were noted as EPD-1 & EPD-2 and after as EPD+1. Weather variables were converted into weekly values and correlated with the stage of flower and acorn production. Analysis of variance, linear regression, the Pearson product-moment correlation and a Bonferroni multiple comparison test were used. Results indicated a significant negative correlation for both populations for maximum temperature and the number of days with hail during the pollination and also the white oak flower survival in July whith rain during the pollination. but the flower survival in early July was positively correlated with acorn porduction in both tree species. Size of flower crops and the dates when flowers aborted showed variations from tree to tree and year to year. 1997 Cecich described the continuum between flowers and acorns, which depends upon successful pollination and fertilization by pollen produced in the staminate flowers. Further Larsen and Cecich (1997) developed a stochastic model for oak flower dynamics. Figure 1 presents model factors affecting each component of acorn production. Larsen and Cecich used this model for exploring the consequences of assumed changes in the factors affecting acorn production. Krannitz and Duralia (2004) explained the cone and seed production in Pinus ponderosa are very variable. There were differences between years, sites and individual trees. Further cone crop could decrease due to physiological factors and insect damage. Temperature during seed cone initiation is important. Sorensen and Webber (1997) used a log-log function (log Y = log a + b log X) to model the relationship between seed yield (Y) and pollen captures (X). Results showed, that seed production in conifers increases rapidly with initial increase in pollen capture, and closely reaches an asymptote at pollen capture values. This values are low compared with maximum PCs measured in field stations.
