Hybrid Douglas-Fir Trees Hold the Key to Climate Change Adaptation

As the world faces the unprecedented challenges of climate change, scientists are searching for ways to help forests adapt to the new normal. A recent study by Compton and colleagues, published in AoB PLANTS, sheds light on how hybrid Douglas-fir trees could be more resilient to climate change and better suited for reforestation efforts.

Douglas-fir trees are a crucial species for timber production and ecosystem services in North America. They provide habitat for wildlife, stabilize soil, and sequester carbon. However, as the climate warms, these trees are threatened by increasing drought and heat stress. In response, researchers have been exploring the genetic variation within the species to identify the best trees for planting in the face of an increasingly challenging environment.

The study’s authors focused on the relationship between growth, water use efficiency, and heat tolerance in different varieties of Douglas-fir trees. Their results revealed a trade-off between growth and heat tolerance. In other words, faster-growing trees from warmer climates are less able to withstand heat stress than their slower-growing counterparts from colder climates.

The researchers also discovered that intervarietal hybrid families, with mixed ancestry from coastal and interior varieties, had higher water use efficiency and greater heat tolerance than pure coastal families. This suggests hybridization might be a source of pre-adapted alleles to extreme heat events and drought in an increasingly warming climate. The study further revealed significant genetic variation in water use efficiency, photosynthetic capacity, growth, and tolerance of leaves to heat stress among Douglas-fir families and varieties. In their article, Compton and colleagues write:

Warmer climates bring significant challenges to the survival of Douglas fir populations. While coastal varieties are widely planted due to their fast growth, their low water use efficiency (a trait of mesic-adapted plants) and low tolerance to heat might predispose them to maladaptation to future climate conditions, as suggested by trade-offs between growth, water use efficiency and heat tolerance found in this study. Our study indicates significant genetic variation in water use efficiency (inferred from carbon isotope discrimination), photosynthetic capacity (inferred from %N), growth and tolerance of leaves to heat stress among Douglas-fir families and varieties. High elevation families had higher water-use efficiency and photosynthetic capacity than low elevation families. In addition, families with greater heat tolerance had slower growth and higher water-use efficiency. Intervarietal hybrids, with mixed ancestry from coastal and interior varieties, had higher water use efficiency and higher heat tolerance than coastal families, suggesting hybridization might be a source of pre-adapted alleles to extreme heat events and drought in increasingly warming climate conditions.

Compton et al. 2023

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Compton, S., Stackpole, C., Dixit, A., Sekhwal, M.K., Kolb, T. and De la Torre, A.R. (2023) “Differences in heat tolerance, water use efficiency and growth among Douglas-fir families and varieties evidenced by GWAS and common garden studies,” AoB PLANTS, 15(2), p. lad008. Available at: https://doi.org/10.1093/aobpla/plad008.