Frequently asked questions (FAQ) about ForestGALES

Does ForestGALES work with mixtures?

The current version of ForestGALES models the effect of the wind on stands that are assumed to consist of identical trees. It's suggested that in mixtures that the risk of wind damage to each component is calculated separately, using the top height and mean diameter of the component, and the average spacing based on the whole crop (i.e. all components of the mixture). The risk to the stand as a whole can be considered to be highest risk for any component, since if one species is damaged then the resulting gaps will increase the risk of damage to the remaining trees.

Does ForestGALES work outside Britain?

The mechanisms by which trees are damaged by the wind are similar throughout the world. However the relationships between diameter and crown size, the resistance of trees to overturning and the wind climate will differ from country to country.

The current version of ForestGALES was designed for British conditions, but it has been successfully adapted for use in New Zealand, south-west France, Denmark, Canada (Quebec and British Columbia), and Japan. ForestGALES 2.5 includes a research mode that allows input parameters and wind climate to be easily modified for other countries.

What does ForestGALES calculate?

ForestGALES calculates the probability of average trees being damaged within a stand. Damage to the average tree will by implication mean that the stand as a whole will be substantially damaged.

How does ForestGALES compare to the Windthrow Hazard Classification (WHC)?

ForestGALES estimates the chance (or probability) of windthrow or stem breakage, rather than stating a precise height at which damage will occur as in the WHC. Probabilistic predictions are more realistic than precise heights since the occurrence of damaging winds varies from year to year, which has a powerful influence on the occurrence and spread of damage. The risk of damage is dependent on the windiness of the site. In the WHC the measure of windiness is much coarser than is used in ForestGALES. This allows ForestGALES to discriminate several levels of risk for trees in similar WHC classes. A study of actual storm damage indicated that stands can be grown for longer than if they were managed using the WHC.