Thinning is normally undertaken every 5 to 10 years once a woodland is 15 to 30 years old. When to start and the frequency depends on a range of factors – the faster the growth rates the sooner and more often trees can be thinned. Care needs to be taken when thinning a woodland to minimise the damage to trees that are being retained.
Tree thinning increases both the overall capital value as well as the regular income that can be obtained for timber from many woodlands. Make it work for your business by supporting your commercial objectives. Thinning and other types of active woodland management can support the transition to continuous cover forestry systems, while creating an opportunity to have a diversity of tree species providing added robustness against climate change, pests and diseases.
The usual method of thinning involves deciding which trees are to be retained and then working to give them enough light and space to thrive. Normally this means removing those with less straight stems, with cracks or defects, tight and weak forks or the less vigorous and less healthy. The number of trees removed in each thinning ranges between 15% to 30% dependent on factors such as exposure to wind, species, soils and stocking levels. The trees to be removed are either pre-marked with a paint blaze, or alternatively foresters select trees as they work through the wood – both methods have advantages.
There are several different methods, from systematic line thinning where entire rows are removed, to more time intensive systems that focus on the trees left within the canopy. It is very important to ensure that regeneration and restocking can occur.