Climate change impacts on drought-prone forests in western Canada

Abstract

From a climate change perspective, much of the recent international focus on forests has been on their role in taking up carbon dioxide (CO 2 ) from the atmosphere. The question of climate change impacts on forest productivity is also emerging as a critical issue, especially in drought-prone regions such as the western Canadian interior. Because of the complexity of interacting factors, there is uncertainty even in predicting the direction of change in the productivity of Canada's forests as a whole over the next century. In the most climatically vulnerable regions, however, successful adaptation may require more innovative approaches to forest management, coupled with an enhanced capacity for early detection of large-scale changes in forest productivity, dieback and regeneration.Key words: climate change, boreal forest, productivity, drought, impacts, adaptation RÉSUMÉ Dans le cadre des changements climatiques, la majeure partie de l'attention internationale récente sur les forêts a porté sur leurs rôles d'emmagasiner le dioxyde de carbone (CO 2 ) en provenance de l'atmosphère. La question des effets des changements climatiques sur la productivité forestière constitue également un enjeu majeur, surtout dans les régions sujettes à la sécheresse comme la partie intérieure de l'Ouest canadien. À cause de la complexité des facteurs en interaction, il existe une incertitude même dans la prédiction de la direction des changements dans la productivité des forêts canadiennes dans son ensemble au cours du prochain siècle. Dans le cas des régions les plus susceptibles en terme climatique, une adaptation réussie pourrait nécessiter des approches plus innovatrices en matière d'aménagement forestier, associées à une capacité accrue de détection hâtive des changements à grandes échelles dans la productivité forestières, le dépérissement et la régénération.

No growth stimulation of Canada’s boreal forest under half-century of combined warming and CO 2 fertilization

“…Projections of future climatic drying pose a major concern for Canada's boreal forest ecosystems (9), especially in the western Prairie Provinces where forest distribution and ecosystem functioning are strongly moisture limited (32). In many Canadian areas, the trends in forest growth were consistent with the directional trend in soil moisture ( Figs.…”

Integrating climate change adaptation into forest management

“…Most of the wood that will be harvested in Canada over the next 50 to 100 years will come from trees that are already growing or will be planted in the next decade with minimal climate change adaptation considerations. In some areas there will be an increase in forest productivity while in other areas there will be a decrease (Spittlehouse 2003, Hogg and Bernier 2005, Johnson and Williamson 2005. What will this mean for rotation ages, wood quality, wood volume, size of logs and determining the annual allowable cut?…”

“…Changes in temperature and precipitation regimes will mean that we will have to revise where and how planting stock and site preparation techniques are used. Species have a wide range of occurrence and it would be prudent to initially target areas near the edge of a species range where the earliest impacts are likely to occur (Hogg and Bernier 2005). In some cases we may have to return to existing second growth stands where the current regeneration is unacceptable as a source for the future forest and replant with other species or genotypes (Woods et al 2005).…”

“…These changes would significantly affect forest ecosystems and their utilization by society. Predicted changes include the movement of species ranges northward and up in elevation, new assemblages of species occurring in space and time, and changes in disturbance regimes, forest productivity and water resources (Stewart et al 1998, Kirschbaum 2000, Dale et al 2001, Mote et al 2003, Gray 2005, Hogg and Bernier 2005, Johnson and Williamson 2005, Volney and Hirsch 2005. Forest management decisions are usually based on the assumption that the climate remains relatively stable throughout a forest's life.…”

National circumstances in the international circumboreal community

“…However, at least once in the past, a climatic warming led to a very rapid transformation of the forest tundra to forest (MacDonald et al 1993). It has been suggested that forest stands, once established, do not much respond to small changes in climate, and that the bulk of the response to climate change may come in the form of regeneration failures or stand type changes following disturbances (Hogg 1997, Hogg and Schwarz 1997, Hogg and Bernier 2005. Poor regeneration of forest following fire has been observed along the southern boreal/grassland boundary (Hogg 1997) and in climatically dry areas of the southwestern Yukon (Hogg and Wein 2005).…”