A probability model for root and butt rot in Picea abies derived from Norwegian national forest inventory data

ABSTRACT

Root rot in Norway spruce (Picea abies (L.) Karst.) causes substantial economic losses to the forestry sector. In this study, we developed a probability model for decay at breast height utilizing 18,141 increment cores sampled on temporary plots of the Norwegian National Forest Inventory. The final model showed a good fit to the data and retained significant relationships between decay and a suite of tree, stand and site variables, including diameter at breast height, stand age, altitude, growing season temperature sum (threshold 5°C), and vegetation type. By comparing model predictions with recorded decay at stump height in an independent data set, we estimated a proportionality function to adjust for the inherent underestimation of total rot that will be obtained by applying a probability model derived from increment cores sampled at breast height. We conclude that the developed model is appropriate for national and regional scenario analyses in Norway, and could also be useful as a tool for operational forestry planning. This would however require further testing on independent data, to assess how well the new model predicts decay at local scales.

KEYWORDS:

• Decay
• Heterobasidion annosum
• probability model
• Picea abies

Acknowledgements

The authors extend their gratitude to the funding bodies Utviklingsfondet for skogbruket and Skogtiltaksfondet, as well as to the County Governors in Hedmark, Vestfold, Nord-Trøndelag and Sør-Trøndelag counties, for funding this work. We also thank Olvar Bergland at the Norwegian University of Life Science for guidance in categorical data analysis. We would also like to acknowledge two anonymous reviewers who provided helpful comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Gro Hylen http://orcid.org/0000-0001-8483-101X

Aksel Granhus http://orcid.org/0000-0002-1713-9928

Additional information

Funding

This work was supported by Skogtiltaksfondet; Utviklingsfondet for skogbruket; County Governors in Hedmark, Vestfold, Nord-Trøndelag and Sør-Trøndelag counties.