Recovery of planted spruce seedlings from abiotic damage caused by exceptional weather conditions in the boreal forest : Identification of risks associated with site selection and regeneration practices

Abstract

Extreme weather events are predicted to increase in the Nordic boreal region with climate change, and stress conditions can damage newly planted seedlings and affect future stand development. The aim of the study was to investigate the recovery of Norway spruce (Picea abies (L.) Karst.) container seedlings from winter and drought damage in southern and central Finland (60–64°N) and the effect of damage on regeneration outcome three growing seasons after damage. Abiotic damage reduced the number of planted spruces (over 1600 trees ha−1) to an average of 1500 planted crop trees ha−1 three years after damage. Natural regeneration supplemented the stands and regeneration outcomes were good (>1600 trees ha−1) in most of the stands. Abiotic damage reduced planted spruces quality, increased the number of multiple stems, and further reduced planted tree growth. Weather conditions had an effect on the recovery of drought-damaged seedlings, but not on the recovery of winter-damaged seedlings. Fall planting, packing growing seedlings in closed cardboard boxes during summer and fall, and planting growing seedlings from outdoor winter storage in dry conditions in early summer reduced seedling recovery from abiotic damage. The use of open geospatial data is promising to identify regeneration sites at high risk of abiotic damage (dry sites and high topographic position). In conclusion, good regeneration results in a changing climate can be achieved by making the right decisions during the regeneration process and by using natural regeneration to supplement planted spruce stands.