Mast-fruiting in Hickories and Availability of Nuts

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Abstract
Variation in nut production, insect infestation of nuts and number of viable nuts were measured in pignut hickory (C. glabra, Juglandaceae) during 3 fruiting seasons from 1975-1977. The purpose was to analyze how production of individual trees and yearly variation in hickory nut availability determine the quantity of nuts which will be dispersed to become seedlings during some years. The results are consistent with the expected pattern for mast-fruiting tree species: all study trees produced their large crops during the same year (1976) and smaller crops in 1975 and 1977. During each year, insects damaged a similar percentage of the crop regardless of crop size, so that the mast year (1976) did not have a significantly larger portion of its crop escaping predation but it did have a larger number of viable seeds. Within each year, trees showed a similar pattern of nut drop: infested hickory nuts fell by mid-Aug. and viable ones fell primarily from Sept. on. Whereas trees dropped only a minority of their viable nuts early, a smaller percentage of these dropped during the mast year than during nonmast years. Hence, the combination of yearly variation in seed production and temporal variation in viable nut-fall led to a cumulative effect of many hickory nuts available at one time during one of the years and few during the others.