Physiologic plasticity, evolution, and impacts of a changing climate on Pinus contorta

Climate response functions for 125 Pinus contorta populations were updated to assess the impact of 16 climate change scenarios on forest productivity. Productivity was defined as the volume of wood expected per hectare at age 20 and was calculated as the product of predicted individual tree volumes, an initial stocking (1600 trees ha(-1)), and predicted survival. Impact wa s considered according to the transient effects of a changing climate gover ned by (1) physiological plasticity in the contemporary generation and (2) long-term evolutionary adjustments that provide adaptedness and optimize pr oductivity in future generations. Direct short-term plastic responses were geographically complex and had repercussions throughout the species' distri bution even when temperature fluctuations were small (+/- 1 degrees C) and changes in distribution were inconsequential. Evolutionary adjustments amel iorated negative short-term impacts while enhancing the positive. Scenarios that encompassed predictions for global warming produced short-term impact s that were negative in the south and positive in the north, but subsequent evolutionary adjustments projected substantial increases in productivity. The long-term adjustments may require only 1 to 3 generations in the north but 6 to 12 generations in the south, thereby taking between 200 and 1200 y ears.