Effects of winter temperatures on two birch (Betula) species
Abraham J. Miller-Rushing (1, 2, 3) and Richard B. Primack (1)
1. Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA / 2. Corresponding author () / 3. Present addresses: Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, CO 81224, USA; and Department of Biology,
University of Maryland, College Park, MD 20742, USA / Received March 8, 2007; accepted June 14, 2007; published online February 1, 2008
Summary
In Massachusetts, low winter temperatures delay the onset of flowering in black birch (Betula lenta L.), but not in gray birch (B. populifolia Marsh.). During the winter of 2006, male inflorescences and twigs of black birch had higher water contents than those of
gray birch, and the inflorescences of black birch experienced greater frost kill than those of gray birch. Vessels diameters
were greater in black than in gray birch, a difference associated with a higher incidence of winter xylem embolism, as indicated
by reduced xylem hydraulic conductance. In both species, recovery of hydraulic conductance in twigs that survived the winter
coincided with the development of root pressure. Frost kill to male inflorescences or associated damage to plant tissues may
account for the difference between species in the effect of winter temperature on the time of first flowering. In a comparison
of 24 birch species, sensitivity of the first flowering date to temperature was also correlated with water content in male
inflorescences.
