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Ash restructuring

Group selection and underplanting of ash stands to mitigate ash dieback - RMIS 0363


Ash trees are now under threat from possibly the single most devastating forest pathogen ever to hit the post glacial woodlands of Ireland. First discovered in Co Leitrim in October 2012, ash dieback (Hymenoscyphus fraxineus) has been steadily developing in the wider environment. Young, single-species stands of ash can be at particular risk and, left untreated, could be at increased risk. Teagasc and the Woodland Trust in Northern Ireland are collaborating on a 5-year research project aimed at reducing the potential impact of ash dieback on such pole-stage stands.

The site

The first trial site has been established within the Woodland Trust’s Drumnaph Wood, Co Derry/Londonderry, part of the Drumnaph Community Nature Reserve. The 31.9 ha reserve comprises a range of important habitats, including 14.7 ha of ancient woodland. The overall woodland area was extended within the Trust’s ‘Woods On Your Doorstep’ millennium celebration through the planting of an additional 11.8 ha of new native woodland. About four hectares of this relatively young woodland is comprised predominantly of ash.


The recent work programme in the wood has had two primary objectives:

  1. Promoting the vigour of the ash stands through thinning
  2. Diversifying the species composition of the predominantly ash stands through underplanting


The thinning at Drumnaph aims to promote the growth of selected individuals by releasing them from competition. The longer the health of these trees can be maintained, the longer we can maintain the ecological integrity and functions of the woodland. Ultimately the long-term resilience of the woodland lies in achieving a greater degree of species diversity. A group-felling treatment using small coupes, 0.025 – 0.045 ha (approx. 20 – 25 m diameter equivalent), was integrated within the conventional thinning, designed to provide the space necessary to plant a range of other native tree species such as oak, hazel and birch (Figures 1 and 2). Prior to planting, the stumps were treated with a mulcher to prevent coppice resprouting. As the site matures the research project will monitor the impact of light conditions and their changing influence over time on the growth of the underplanted trees with the objective of providing management guidelines for such a silvicultural system. Hopefully this work can inform woodland owners regarding the positive options available to secure the most productive future for their ash-dominated woodlands.

Figure 1: Diagrammatic representation of group felling superimposed on rack and selection thinning (l) and a small replanted coupe at Drumnaph Woods (r)



Figure 2: Drumnaph Woods coupe 3: Ten felling coupes have been installed in Drumnaph Woods (see image). The animated image above illustrates one method being used to monitor the variable light conditions across a felling coupe. Using Coupe 3 as an example, hemispherical photos taken at points (indicated by a red star) along a permanent S-N transect of the coupe illustrate the changing light regime across the coupe. These photos will be repeated over the following years to investigate the impact of the canopy as it grows into the coupe space. 

Project team

  • Dr Ian Short, Project Coordinator and Principal Investigator, Teagasc
  • Derek Gibson, Technician, Teagasc



The Research Field · 11: Broadleaf Tree Plantations Increasing in Ireland


  • Short, I. and Hawe, J. (2018) Management of ash stands to mitigate ash dieback. National Forestry Conference, Enfield. 30/05/2018

Figure 3: Poster presented at National Forestry Conference, Enfield, 30/05/2018