Abstract

• Key messageRoot and rot (RBR) caused byHeterobasidion parviporumNiemelä & Korhonen andHeterobasidion annosum(Fr.) Bref. damages Fennoscandian spruce stands. In case the rot infection and its severity are unknown, the mere risk of infection should seldom affect the harvest timing. When it does, the gains by harvesting earlier are minimal.• ContextIt has been suggested that stands infected by RBR should be harvested earlier than the healthy ones. Yet, we must decide on harvest timing decisions without reliable information on the infection.• AimsWe studied if harvesting earlier pays off under RBR uncertainty.• MethodsWe structured the uncertainty with a decision tree and calculated the optimal rotations based on expected net present values. We compared rotation lengths to those of healthy stands and calculated gains from earlier harvesting.• ResultsThe inclusion of RBR-related uncertainty in the model changed the rotation length of only 14–23% of the stands. The average reduction was 1.3–4.7 years. Yet, the gain from harvesting earlier was too low to be considered.• ConclusionIn the absence of information on the extent and severity of RBR, it seldom pays off to advance harvests. The value growth in healthy trees tends to compensate for the value reduction due to rot.

Highlights

  • The tree pathogens Heterobasidion parviporum Niemelä & Korhonen and Heterobasidion annosum (Fr.) Bref. causes root and butt rot (RBR) in Fennoscandian coniferous forests, mainly Norway spruce

  • By comparing the harvest age of the simulations with and without rot, we found the impact of considering RBR-related uncertainty on the economically optimal rotation age of stands

  • By including RBR uncertainties in the calculations, the optimal rotation age differed from the simulation without rot in 14% of the stands (Fig. 2a) when simulating both 3 and 2% interest rates

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Summary

Introduction

The tree pathogens Heterobasidion parviporum Niemelä & Korhonen and Heterobasidion annosum (Fr.) Bref. causes root and butt rot (RBR) in Fennoscandian coniferous forests, mainly Norway spruce Causes root and butt rot (RBR) in Fennoscandian coniferous forests, mainly Norway spruce In Nordic conditions, the decay can reach up to 10–12 m in height (Stenlid and Wästerlund 1986) making RBR harmful as it destroys the most valuable part of the tree, downgrading it from sawn wood quality to pulp or energy wood (Pukkala et al 2005; Seifert 2007). A nationwide stump survey carried out in 1992 showed that, on average, every 5th harvested spruce in Norway had stem decay caused by Heterobasidion annosum (Fr.) Bref. A probability model for RBR infection in Norway spruce was developed explicitly for Norwegian conditions (Hylen and Granhus 2018)

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