Using spruces (Picea spp.) for Icelandic afforestation

Afforestation can help address climate change and biodiversity loss. Iceland is a valuable case study to assess afforestation at extreme locations at high latitudes (63–68°N). We used a ~ 23-year dataset of a provenance trial from the Icelandic Forest Service (now Land & Forest Iceland) to determine the best spruce species (Picea spp.) and provenances for afforestation. Sites were either frost-prone or protected (i.e., non-frost-prone) locations, and the latest height and survival data were assessed from six sites (out of nine) in 2018. Provenances were mainly from three spruce species from southwestern Canada and southern Alaska (53–61°N). Sitka spruce (Picea sitchensis) and its hybrids or introgressants with white spruce (P. glauca) survived and grew well in protected areas (≥ 60% and ≥ 275 cm), while white spruce and its hybrids or introgressants with Sitka spruce performed better in frost-prone areas (≥ 55% and ≥ 285 cm, based on combined frost-prone sites). The only provenance suitable for both frost-prone and protected places was a Sitka/Lutz spruce (P. x lutzii) introgressant from Iniskin Bay, Alaska. Additional genetic research would help guide afforestation in harsh areas at high latitudes (a distributional limit of many tree species) and inform forest management about novel environments and sustainable practices. Climate change should also be considered for afforestation efforts.