Moving up north: How do translocated seedlings perform in mixed-species plantings at the boreal-temperate interface?

Abstract

Climate change is forcing us to find innovative solutions to help managed forests cope with rapidly shifting environmental conditions. One of these tools is assisted forest migration, the deliberate movement of individuals or genetic material from native sources (i.e. provenance) to locations within or beyond their current ranges. This study aims to assess the climate analogue concept as seed sourcing method in an assisted migration field trial. We evaluated the five-year survival and growth of nine species in mixedwood plantings established in 2018 in Quebec, Canada. The factorial experimental design comprised cutting treatments (1.2 ha patch clearcut vs. 40 % uniform shelterwood), cervid exclusion (excluded vs. non-excluded) and competing vegetation (brushcut vs. control) treatments. Seedlings were grown from seeds of locations associated to three climate analogues: current climate, projected climate for mid-century (2041–2070) and end-of-century (2071–2100). Five-year survival averaged 84 %, ranging from 69 % for Carya ovata to 90 % for Quercus rubra. End-of-century analogue performed less well than others for relocations > 500 km. All species grew larger in patch clearcut than in shelterwood, especially Pinus, Picea and Thuja spp. (3–4× diameters, 2–3× heights). To a lesser extent, brushing slightly improved diameter growth of Carya ovata, Quercus rubra and Thuja occidentalis, but only in patch clearcuts for Prunus serotina, Pinus and Picea spp. Impact of cervid was minimal likely due to snowpack protection. We observed limited effects of climatic mismatch on translocated seedlings, which supports the climate analogue approach as seed sourcing method. Longer-term monitoring will be required to confirm trends.