The Adaptive Tradeoffs between Boreal and Temperate Conifers in a Warming World
In a warming world, trees growing in seasonally cold environments may encounter new winter stresses associated with delayed acclimation, midwinter deacclimation, winter respiration, and light stress, even if they are well-adapted to surviving low-temperature stress in existing climatic regimes. Boreal and temperate conifers that maintain foliage through the winter months may be especially vulnerable. Therefore, an understanding of the timing and mechanisms of natural frost hardening and other physiological processes during winter will be important in predicting the effects of global warming on tree and forest health and productivity.
Through a series of field and laboratory-based experiments, we are examining the basic biological mechanisms of conifer cold tolerance and winter carbon relations. In particular, we are 1) evaluating the role that foliar sugars play in developing and maintaining freezing tolerance, and 2) exploring the possible tradeoffs between maintaining cold tolerance and remaining physiologically inactive versus reducing cold tolerance and increasing physiological activity (e.g., photosynthesizing and capturing carbon) as traditionally cold seasons (fall, winter and spring) warm.
Preliminary data suggest that boreal conifers develop and maintain extreme cold tolerance during winter, and that this protects them from freezing injury under all likely extremes in winter low temperatures. However, to maintain this extreme hardiness, these species also concentrate sugars at such high levels that photosynthesis is down-regulated – limiting possibilities for carbon capture during the cold season – even during warm spells. In contrast, temperate conifers appear to develop less cold hardiness, but retain the capacity for carbon capture when temperatures become more moderate – even during midwinter. More complete analysis of the responses of boreal and temperate conifers to climatic warming will allow for better modeling of apparent tradeoffs between cold hardiness and carbon capture. A better understanding of the competitive roles of boreal and temperate conifers will allow managers to judge where and when to favor these adaptive types in order to maximize productivity and carbon sequestration as climates warm.
Strimbeck, G.R., and Schaberg, P.G. 2009. Going to extremes: Low-temperature tolerance and acclimation in temperate and boreal conifers. In: L. Gusta, M. Wisniewski, and K. Tanino, Eds., Plant Cold Hardiness: From Laboratory to the Field, CAB International Publishing, Wallingford, UK.
Strimbeck, G.R., Kjellsen, T.D., Schaberg, P.G., Murakami, P.F. 2008. Dynamics of low-temperature acclimation in temperate and boreal conifer foliage in a mild winter climate. Tree Physiol. 28:1365-1374.
Strimbeck, G.R., Kjellsen, T.D., Schaberg, P.G., Murakami, P.F. 2007. Cold in the common garden: comparative low-temperature tolerance of boreal and temperate conifer foliage. Trees: Structure and Function. 21:557-567.
- Paul Schaberg, USDA Forest Service - Northern Research Station, Research Plant Physiologist
- Paula Murakami, USDA Forest Service - Northern Research Station, Research Associate
- G. Richard Strimbeck, Norwegian University of Science and Technology, Professor of Biology
- Trygve Kjellsen, Norwegian University of Science and Technology, Ph.D. Candidate
Last Modified: 02/04/2010