Tree stability and climate


Example of wind damage to woodlandRecent research has improved our understanding of the fundamental processes involved in windthrow. The tree stability and climate programme provides management tools, advice and knowledge to reduce wind damage to British forests.

The threat of wind damage is widely recognised to be a serious constraint to the management of British forests.  Major storms have caused volumes of timber in excess of 1m m3 to be damaged at least five times in the last 50 years. The risk of windthrow is a major determinant of rotation length in upland Britain and thinning programmes are constrained in over 50% of regions because of wind damage. Wind damage is believed to cost countries in the European Union approximately 15 million Euros per year, and on occasions substantially more. For example, storms in Northern Europe in December 1999 overturned more than 300 million m3 of timber and in January 2005 overturned more than 85 million m3 of timber.

Pulling a tree with a power winch in Glentrool ForestPast tree stability research in Britain was influential in the choice of rotation lengths and thinning practice. It has also influenced the choice of operational techniques, such as the move towards use of mounding as an establishment technique for afforestation and restocking, and the abandonment of late mechanical thinning on vulnerable sites.

The fundamental processes involved in windthrow include the interaction of trees and wind, the interaction of roots and soil, and the interaction of wind and topography. This programme has demonstrated the limitations of the Windthrow Hazard Classification that was previously widely used for wind risk decision-making.

Over the last few years a major success has been achieved through the synthesis of tree stability and wind climate knowledge into a computer-based model, ForestGALES, to guide forest managers on the risks of wind to conifer plantations.

Research objectives

The key role of the Tree Stability and Climate programme is currently to develop a version of ForestGALES which is integrated with Arcview GIS. At the same time we are working towards the goal of modifying ForestGALES to enable it to calculate the risk of wind damage to 'alternative silvicultural systems' and mixed species stands.

The main current research objectives are:

  • To understand the interaction between wind, topography and trees and the effect of temporal variability in extreme wind occurrence
  • To improve the representation of the British wind climate in ForestGALES
  • To examine the interactions between the physiological development of roots and soil properties
  • To develop improved relationships between anchorage and tree dimensions, separated between species, soil group and rooting depth
  • To develop a new wind risk model which deals with the risk to individual trees. This will allow calculation of the risk to species mixtures and where alternative silvicultural systems are used.

Funders and partners

Forestry Commission logo
This research is predominantly funded by the Forestry Commission.

EU flag 
The European Commission funded work in the Ecoslopes project on tree stability, and the potential for soil loss, on complex terrain. A current EC project, EFORWOOD, examines wind as an abiotic risk within a Sustainability Impact Assessment of the Forestry - Wood Chain. Windthrow scenario modelling and a development of a research version of ForestGALES were funded as part of the EC Interreg North Sea Region STORMRISK project.

Interreg North Sea Programme logo 

Forestry Commission policy

Research on windthrow has been identified as a component of the UK Programme on Sustainable Forestry. Para 3.28 states the aim "To promote better prediction of the onset of windthrow to optimise the returns from windthrow susceptible sites.". This is consistent with priorities identified by other organisations such as Timber Growers Association (TGA), Home Grown Timber Advisory Committee (HGTAC) and the National Audit Office (NAO).



The programme ran to 2011.


Bruce Nicoll

Last updated: 12/16/2014

What's of interest

A PC and web-based decision support tool that enables forest managers to estimate the probability of wind damage to any conifer stand in Britain.

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