Douglas-fir is an iconic tree in the Pacific Northwest. Although individual trees may appear to be identical, genetic differences within each tree have resulted from adaptation to the local environment. These genetic differences over time have resulted in differences among populations that are important to the species’ survival and growth in changing climates.
Current climate models project that over the next 50 years, the Pacific Northwest will experience an increase in summer temperatures. Combined with less winter snowpack, warmer summer temperatures will likely lead to more frequent and intense droughts, and it is unknown how Douglas-fir will respond. Researchers with the U.S. Forest Service Pacific Northwest Research Station tested how seedlings from different populations of Douglas-fir would grow in temperature and precipitation conditions unlike the climate of their current seed source. By sampling 35 populations in three common garden sites, researchers determined how a combination of genetic factors and environmental conditions influence drought-tolerant traits.
Trees grown in a warm, dry environment had lower rates of water loss compared to seedlings grown in cooler environments. Furthermore, researchers identified populations that had high drought tolerance and relatively fast growth. This means that although Douglas-fir as a species is relatively drought tolerant, some populations are better adapted to future climate conditions than others.