Yellow-cedar and western redcedar ecophysiological response to fall, winter and early spring temperature conditions

Abstract

-Western redcedar (Thuja plicata Donn) and yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) populations originating from an elevation zone where these two species naturally coexist were monitored to define their performance patterns in response to seasonal temperature conditions within the fall, winter and early spring field conditions of the Pacific Northwest coastal forest region. Western redcedar and yellow-cedar populations were measured for changes in growth rhythms, photosynthetic patterns and freezing tolerance. Net photosynthesis (P n ) for both species was directly related to minimum air temperature that occurred during the prior evening, though no population differences were detected within each species. Photosynthesis was greater in western redcedar, than yellow-cedar when minimum air temperature was above freezing. Freezing temperatures from ~0 to -5°C caused a greater reduction in photosynthesis for western redcedar, though not a complete cessation of photosynthetic capability in either species. Freezing tolerance increased at a moderate rate in the fall as mean air temperature declined for both species when their shoot systems were still active, with freezing tolerance increasing at a rapid rate when shoot systems showed no mitotic activity. No shoot growth or mitotic activity was detected in shoot tips of both western redcedar and yellow-cedar when mean air temperature decreased to 4°C for the previous week. No population differences, within each species, were detected in the development of fall freezing tolerance. Yellow-cedar obtained a slightly greater level of freezing tolerance when fall temperatures were < 4°C. Both species had a loss of freezing tolerance as mean air temperature increased in late winter. Shoot growth resumed in both species in late winter when mean air temperature increased to 6 to 6.5°C. The resumption of shoot growth resulted in a faster loss of freezing tolerance for western redcedar compared to yellow-cedar. où ces deux espèces coexistent ont été suivies pour définir leurs types de performances en réponse aux conditions thermiques saisonnières de l'automne, de l'hiver et du début du printemps dans la région forestière côtière du Nord Ouest Pacifique. Les populations de Thuja plicata et de Chamaecyparis nootkatensis ont été mesurées pour étudier les variations dans les rythmes de croissance, les types d'activité photosynthétique et la tolérance au gel. Pour les deux espèces, la photosynthèse nette (Pn) était directement liée au minimum de température du soir précédent, bien que des différences n'aient pas été mises en évidence entre populations dans chacune des espèces. La photosynthèse était plus élevée chez Thuja plicata que chez Chamaecyparis nootkatensis lorsque la température minimum était au-dessus de zéro degré. Les températures glaciales de -0 à -5°C induisent la réduction la plus importante de la photosynthèse chez Thuja plicata, quoiqu'il n'y ait pas un complet arrêt de la capacité photosynthétique chez l'une ou l'autre des espèces. Pour les de...

Tradeoffs between chilling and forcing in satisfying dormancy requirements for Pacific Northwest tree species

“…Species such as Douglas-fir with an obligate chilling requirement are likely to have range restrictions in areas which currently experience warm winters. This is consistent with earlier suggestions that warming could delay budburst if chilling was not adequate (Cannell and Smith, 1986) or result in abnormal development (Chandler et al, 1937; Weinberger, 1967). Although budburst will generally occur much earlier under the 2080 A2-emission scenario we modeled, there are areas in California and on the southern Oregon coast where the date of spring bud burst is predicted to occur later than under current climatic conditions.…”

“…Woody plants generally experience a reduction in forcing (or thermal time) with increased chilling (Cannell and Smith, 1983, 1986; Murray et al, 1989) but the magnitude of the effect differs with species. In addition, since each location has its own climate and species (or genotypes) differ in their chilling requirements, the effects of warming may advance or retard budburst (or result in atypical development) depending on how the winter environment satisfies the plant's chilling requirement (Chandler et al, 1937; Weinberger, 1967; Cannell and Smith, 1983, 1986). More recent studies have also developed or used existing models of dormancy to predict future timing of bud burst associated with climate change (c.f., Murray et al, 1994; Cumming and Burton, 1996; Schwartz and Hanes, 2010).…”

“…More recent studies have also developed or used existing models of dormancy to predict future timing of bud burst associated with climate change (c.f., Murray et al, 1994; Cumming and Burton, 1996; Schwartz and Hanes, 2010). Other studies on dormancy have focused on describing the phenomenon with the goal of managing bare-root or containerized nursery plants in cold storage (van den Driessche, 1977) or selecting horticultural varieties for specific climates (Saure, 1985). …”

Shifting Climate, Altered Niche, and a Dynamic Conservation Strategy for Yellow-Cedar in the North Pacific Coastal Rainforest

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Adaptation to exploit nitrate in surface soils predisposes yellow-cedar to climate-induced decline while enhancing the survival of western redcedar: A new hypothesis

“…The potential habit of producing shallow fine-roots by yellow-cedar was previously described in our conceptual model as a response to wet, anaerobic conditions in these declining forests. Yellow-cedar (Hawkins et al, 1994;Schaberg et al, 2005Schaberg et al, , 2008, and redcedar (Grossnickle and Russell, 2006) break cold-hardiness early in the spring. For at least yellow-cedar, this trait may represent an adaptation to highelevations where snow consistently protects roots during the winter but trees may benefit from rapid growth and physiological activity immediately after spring snowmelt.…”