Forest Service - Thinning

Benefits of thinning

Thinning in conifer and broadleaved woodland involves the removal of part of the crop in order to concentrate future volume growth on fewer and better quality stems. The main aim of thinning is to improve stem quality through the removal of deformed/weaker trees and to reduce the time taken for trees to reach valuable sawlog size. Thinning is the most powerful tool the grower possesses to manipulate the development of the plantation and the quality and log size of the final crop. Thinning will improve overall timber revenue by increasing the volume of sawlog and final crop trees produced. This is due to the fact that larger quality trees generally attract significantly higher prices.

Types of thinning

In conifer woodlands generally every 7th line of trees is removed with some selection in between. This can vary depending on the site and quality of the crop. In broadleaved woodland thinning will also involve removing some lines of trees to allow access for machinery.

Selection of trees involves the removal of deformed and weaker trees throughout the crop. Thinning can be either mechanised or motor manual. In mechanised thinning in conifer woodland, a harvester fells, delimbs and crosscuts the stem into various product assortments, e.g. pulpwood, pallet wood, stake wood and sawlog (usually based on the top diameter and length of the log). The material is then extracted to roadside by a forwarder.

Timing of thinning

The timing of first and subsequent thinnings depends on the productivity of the site. Yield class is used to identify the potential growth rate of plantations. Yield classes vary from 4 to 30 for conifers depending on species and site productivity. A yield class of 20 means that the crop has the potential to produce 20 cubic metres (m3 ) per hectare (ha) per year over a full rotation. Broadleaved crops have lower yield classes in the range of 4 – 8 m3 per ha per year. The higher the yield class, the greater the growth rate, the shorter the rotation and the earlier the age of first thinning.

The timing of first thinning is especially important in Ireland due to our windy climate and the wet mineral soils that so often typify plantations. If delayed, the crop trees can get drawn up and once opened up through thinning could render the crop liable to windthrow. The recommended ages of thinning varies between species and depends on a number of site factors. For example, the recommended age to thin Sitka spruce can range from 14 to 22 years of age. In young broadleaved woodland, the height of trees is used as a guide and first thinning can take place when trees are approximately 8 to 12 metres in height. Forest owners should seek professional advice from a registered forester before making decisions on when and how to thin.

Available Schemes to support thinning operations

Forest Roads Scheme

Forest roads enhance the economic viability of forests primarily by improving access for thinning and clearfell operations. In addition, forest roads also provide areas for stacking, drying and chipping of wood. Forest roads also improve the environmental and biodiversity value of forests by increasing edge effects, improve access to deal with fire and allow for better health and safety by providing access for emergency vehicles.

Grants of up to 100% of eligible costs incurred in the construction of a forest road are available and are paid in a single instalment. The maximum grant rate available is €40 per linear metre and the maximum density of road is 20m/ha. For example a 20 hectare forest could receive grant aid to construct a road 400 metres in length and receive funding of up to €16,000.

Additional supports under this scheme are available for bellmouth entrances, connecting roads and special construction works.

Woodland Improvement Scheme: Thinning and Tending of Broadleaves The ‘Woodland Improvement Scheme:

Thinning and Tending’ (WIS) provides financial support for woodland improvement work associated with tending and thinning of young broadleaved woodland planted under grant aided afforestation schemes.

The broadleaf thinning and tending operations allow the improvement of existing grant aided woodlands. The WIS is 100% funded by the Exchequer and is approved by the EU as part of the Forestry Programme 2014 -2020. A fixed grant of up to €750 per hectare is available as a single payment under the Scheme.

Details of the Schemes and grants may be obtained from: Approvals Section, Forest Service, Department of Agriculture, Food and the Marine, Johnstown Castle Estate, Co. Wexford, Y35 PN52 Tel: 053 9163400 or 0761 064415


Website: grantsandpremiumschemes2015-2016/

Requirement for Felling Licence

The felling of trees is regulated by the Forestry Act 1946 and a felling licence is required. The Forestry Act 2014, enacted in October 2014, will, when commenced, replace the Forestry Act 1946. The requirement for a Felling Licence will remain under the Forestry Act 2014.

Application forms are available from:

Felling Section, Forest Service, Department of Agriculture, Food and the Marine, Johnstown Castle Estate, Co. Wexford, Y35 PN52. Tel: 053 9170371



  • From the Forest Service News, Issue 14, January 2017