In general, the primary goal for coastal Douglas-fir breeding is to improve volume production at rotation while maintaining wood density at the population level. This breeding program currently uses recurrent selection; however, genomic selection approaches, especially for more mature traits, are being explored as is screening for Swiss needle cast, a needle fungal disease, that is expected to become more prevalent with climate change.
Tree improvement and breeding efforts in coastal Douglas-fir are restricted to three seed production units.
SPU 1 ranges from 0 to 900 metres elevation in coastal areas west of the Coast Mountains. It is the most important coastal Douglas-fir SPU. In this area, roughly 10 million trees are planted annually with seed produced in orchards. In SPU 1, seed orchards are now at third-generation selections, with anticipated genetic gains of 25 to 30 percent (volume gain at rotation of age 60).
SPU 19 is smaller than SPU 1. It is in the coastal-interior transition (sub-maritime) zone at an elevation band between 400 and 1100 metres. Seed use in this zone is roughly 1 million seedlings per year.
SPU 31 is a minor component in coastal high-elevations between 900 and 1200 metres. Only 0.5 million seedlings are planted per year.
The genetic gains in SPUs 19 and 31 are more moderate than in SPU 1 (7 to 15 percent), and come from backward selections based on progeny testing.
References
A 2nd generation coastal Douglas-fir progeny test, fenced to protect against deer browsing.