Ecophysiological investigations of understory eastern redcedar in central Missouri.

Eastern redcedar (Juniperus virginiana) is a sun—adapted, drought—resistant pioneer species common to pastures, abandoned fields, fence rows, and calcareous rock outcrops throughout the eastern United States. However, it is also a frequent component of the understory in mature oak—hickory forests in central Missouri, where light levels are typically <10% of full sunlight during much of the growing season. This is below eastern redcedar's reported optimum for photosynthesis. The competitive survival of understory eastern redcedar under such environmental conditions was apparently due to it being an evergreen conifer in a deciduous forest. Hence, its foliage was able to maintain a positive carbon dioxide balance throughout much of the year, with maximum net photosynthetic rates occurring during periods when the overstory was leafless. The greatest daily average net photosynthetic rates (Phn) occurred during overstory leaf emergence when temperatures were moderate and light levels to the understory trees wer...