Physiological processes during winter dormancy and their ecological significance
Lengthy and severe winters require that trees in the forests of boreal and mountain zones undergo winter dormancy. Physiologically, a high resistance to subfreezing temperatures and concomitant dehydration are necessary. To accomplish this dormancy, both physiological and structural changes are needed at the cellular level that require induction by endogenous and photoperiodic control early in autumn. Endogenous rhythmicity promotes cold hardening in early autumn and the persistence of hardiness throughout the winter. Numerous physiological functions are maintained at a reduced level, or become completely inhibited during true winter dormancy. Winter hardiness also includes the capability to minimize water loss effectively when water uptake is severely impeded or impossible. Anatomical features such as tracheids act to minimize xylem embolism during frequent freeze-thaw cycles, and {open_quotes}crown{close_quotes} tissues enable buds to stay in a dehydrated and, thus, more resistant state during winter. Both these structural features are adaptations that contribute to the dominance of conifers in cold climates. Interestingly, deciduous tree species rather than evergreen conifers dominate in the most severe winter climates, although it is not clear whether limitations during winter, during the summer growth period, or during both are most limiting to conifer tree ecology. Additional work that evaluates the importance of winter and summer growth restriction, and their interaction, is needed before a comprehensive understanding of conifer tree ecophysiology will be possible.
- Research Organization:
- Wyoming Univ., Laramie, WY (United States). Dept. of Botany
- OSTI ID:
- 62352
- Report Number(s):
- DOE/ER/61253-1-Vol.1; CONF-9109550-Vol.1; TRN: 95:004108-0005
- Resource Relation:
- Conference: Workshop on physiological ecology of coniferous forests, Laramie, WY (United States), 16-19 Sep 1991; Other Information: PBD: 1995; Related Information: Is Part Of Ecophysiology of coniferous forests; Smith, W.K. [ed.] [Univ. of Wyoming, Laramie, WY (United States). Dept. of Botany]; Hinckley, T.M. [ed.] [Univ. of Washington, Seattle, WA (United States). Coll. of Forest Resources]; PB: 351 p.
- Country of Publication:
- United States
- Language:
- English
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