A comparison of Sitka spruce x white spruce hybrid families as an alternative to pure Sitka spruce plantations in upland Britain

The heavy reliance of British forestry on Sitka spruce (Picea sitchensis (Bong.) Carr.) presents a risk in a time of changing climate and increasing incidence of pests and diseases. Three experiments were established in 1987 to examine alternative species including hybrids of Sitka spruce and white spruce (Picea glauca (Moench) Voss.) (SS x WS). After 29 years, the height and diameter growth of the best-performing hybrid families was as good as that of unimproved Queen Charlotte Islands (Haida Gwaii) Sitka spruce at two sites, with slightly reduced diameter growth being the only difference at the third site. The SS x WS hybrid families also outperformed white spruce and Engelmann spruce. Performance of the hybrid families was variable and strongly associated with parentage; selection of both female and male parents should be an important consideration in any future research and breeding programmes. There was no evidence that the hybrid families performed disproportionately well at the drier of the three sites and further work would be required to investigate relative drought tolerance. The results show that the SS x WS hybrid families could be an alternative to Sitka spruce and contribute to increasing forest diversity to develop more resilient forests.