Abstract

Keywords

windfall, stand dynamics, Methods: comparative study, comparative study

Abstract

The influence of site factors and stand structure on wind damage to forests by the storms Vivian in 1990 and Lothar in 1999 was examined using classification tree methodology. More than 400 systematically located inventory plots within the area affected by both storms, covering approximately two thirds of the forest area in Switzerland, were used in the analysis. Within the area 17% of the plots showed signs of damage by Vivian and 37% by Lothar. Classification tree methodology was used to recursively partition the data set into damaged and undamaged sites. Using ten-fold cross-validation, overall classification accuracy was around 80% for the Vivian storm and 65% for the Lothar storm. For both storms the probability of damage increased with stand height, development stage, percentage of conifers, soil-water logging and soil depth. Damage was higher on hilltops, in plains or on gentle slopes, while irregularly structured stands had lower probabilities of storm damage. For the Lothar storm, forests with prior damage from Vivian or where recent felling had taken place were particularly likely to suffer storm damage. The variables used for splitting and the direction of the splits were similar for both storm events. Although overall accuracy was between 65 and 75%, it was not possible to predict the proportion of damaged stands correctly when the model fit for one storm was validated against the findings for the other storm. Information on wind speed could be included in future models to improve prediction accuracy.

LWF Classification

Network: Sanasilva, Category: ISI,