Annual, Local, and Individual Variation in the Inflorescence and Fruit Production of Eastern Leatherwood (Dirca palustris L. Thymelaeaceae)

Abstract

through time when vegetative growth must also be supported from a limited pool of photosynthate. We compared reproductive performance characteristics among natural stands in Upper Michigan, USA across seven years. In addition, we inquired whether small or deeply shaded shrubs tended to be less consistent fruit producers. Fruit set fluctuated considerably over the period, but several conspicuously good and poor years did not correspond to temperature patterns. Flower production was largely stable at the stand level over the seven year period, with increases in years 2000 and 2001. Fruit production was a function of shrub size and did not differ between years or between stands. At an individual level, small and deeply shaded individuals tended to have one or two conspicuously good fruiting years against a background of low fruit production; sunlit and larger individuals were more consistent fruit producers. Fruit production was not related to the previous year's fruit crop. Shrub size and, secondarily, light availability were the important determinants of fruit production, implying that stand age and history govern the population recruitment of leatherwood.