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Title: Influence of weather on pollination and acorn production in two species of Missouri oaks
Author: Cecich, Robert A.
Publication: In: Pallardy, Stephen G.; Cecich, Robert A.; Garrett, H. Gene; Johnson, Paul S., eds. Proceedings of the 11th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-188. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 252-261
Abstract: The process by which oak pistillate flowers become acorns is reasonably understood from an anatomical perspective; however, the way that various factors influence this process is still unclear. This study examined acorn production in a small population of white oak and black oak trees in central Missouri, from 1990 to 1995, in relation to weather variables (maximum and average temperature, relative humidity, fog, rain, and hail) at the time of pollination. There was large tree-tree and year-year variation in the size of flower crops and the dates when the flowers aborted. In the white oaks, acorn production was never high in relation to the number of flowers produced; most flowers aborted by July every year. The black oaks generally produced more acorns than the white oaks, but some individual trees never produced a mature acorn from their large flower crops. This variation in acorn production is correlated with certain weather variables at the estimated time of pollination and for the 1 or 2 weeks before and after those dates. Significant negative correlations with black and white oak acorn production were found for maximum temperature and the number of days with hail during pollination. Rain during pollination was negatively correlated with white oak flower survival in July. In both the black and white oaks, flower survival in early July, following pollination, was positively correlated with acorn production.
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