Broadleaf forestry for Irish growers

Over the past decade, native broadleaves have accounted for approximately one third of afforestation programmes in Ireland compared with less than 5% for most of the last century. In forestry terms, this represents a seismic silvicultural shift in species selection, which deserves analysis.

The recent resurgence in broadleaf planting and woodland conservation, is more than an emotional expression by landowners – mainly farmers – that this lost resource needs to be restored, laudable though that objective is.

The availability of better quality land necessary for growing most broadleaves, attractive grants and premia and the achievement of greater woodland biodiversity have all been advanced as reasons for planting broadleaves. Forest owners in Ireland believe that conifers provide greater economic benefits than broadleaves and if managed correctly can also provide biodiversity and other non-wood benefits. But, in reality, the debate between coniferous and broadleaf forestry is no longer relevant as an increasing number of forest owners see a role for both in achieving multipurpose forestry goals.

Foresters and forest owners strive to plant the right trees in the right places to achieve economic and environmental goals. Forestry guides and manuals such as A Guide to Forest Tree Species Selection and Silviculture in Ireland (Horgan et al) don’t differentiate between broadleaves and conifers. They provide the information and let the reader decide on eventual species composition based on site suitability and clearly defined objectives. However, the goals and objectives differ between broadleaf and coniferous forestry which were outlined in a previous COFORD publication Growing Broadleaves. It provided guidelines for five native and naturalised broadleaves comprising ash, oak, sycamore, cherry and beech.

The authors at the time believed that a more comprehensive book was required to cover a wider range of broadleaves. As a result, three of the authors – Dr Richard MacCarthy and professors emeriti Dr Padraic Joyce and Dr Jurgen Huss – were joined by John Fennessy to research and produce the follow-up to Growing Broadleaves. What has emerged is Broadleaf Forestry in Ireland, which has broadened the species palette and trebled the content to 496 pages of tightly-knit prose and ample illustrations.

The book is divided into two parts: development, site demands, objectives and silviculture of broadleaves (part one); and species description (part two). Part one is sub-divided into five sections beginning with the development of broadleaf forestry in Ireland from the last Ice Age up to the present. The second section addresses site suitability, including climatic factors, soils and the inter-relationship between broadleaf species and site conditions. It also covers issues dealing with the ever-shifting economic, ecological and social grounds of broadleaf forestry. The section dealing with silvicultural practices is deserving of a book in its own right covering 160 pages and deals with species characteristics, establishment, silvicultural management, crop improvement and harvesting.

In part two, the most obvious difference between Growing Broadleaves and Broadleaf Forestry in Ireland is apparent in the number of species covered. The number has increased from five to 63, comprising 25 “main producing broadleaf species” and 38 “minor” species, not including over 100 broadleaf species which the authors feature as a farewell round-the-world tree trip as the winning post looms into sight.

But, in truth, less than a dozen broadleaf species are relevant to Ireland as woodland or timber trees. Since the threatened demise of ash, the list of native species is limited to sessile and pedunculate oak, common alder, birch, sourced from genetically improved material, and group planting of cherry. Add non-native but naturalised species such as beech, sweet (or Spanish) chestnut and sycamore to a few exotic broadleaves with potential and the list is complete.

The authors are cautious in advocating exotics, preferring to keep their options open. Red alder for example “merit[s] further investigation” while Italian alder is “deserving of further trial plantings”. The book is at its best when it deals with specific issues such as site productivity, species selection and crop establishment. It is also on solid ground as it adopts a guide-like role when addressing subjects such as tending and thinning broadleaf stands. The coverage of silvicultural systems includes, clear-cut, shelterwood – uniform and irregular – single tree selections and combinations as well as coppice systems. ProSilva Ireland, the organisation that advocates close-to-nature permanent forest management, will be disappointed with the views expressed on continuous cover forestry (CCF), which the authors claim “cannot be clearly defined as it contains elements of all the silvicultural systems for high forests, except the clear-cut system”.

While the title refers specifically to broadleaf forestry in Ireland, the book trawls widely. Illustrations lean heavily on continental woodlands and management practices and, in this regard, the authors might have sourced more Irish examples, including some of the excellent broadleaf forests established by winners of the RDS-Forest Service Forestry Awards since its inception in 1987 and CCF.

Clarity

The authors address virtually every element of broadleaf forestry comprehensively and, for the most part, with clarity and conviction. Occasionally, the Irish reader may be confused when applying the authors’ recommendations to current management practices, especially relating to plant spacing or density when establishing broadleaf crops. For example, they recommended 6,600 plants/ha for beech and oak, while also including an extravagantly broad range of 4,000 to 10,000 (Table 1). They make the case for high densities for oak and beech which don’t self-prune to the same extent as sycamore, alder and birch. They could also have made a case for sweet chestnut, which has similar branching characteristics as beech and oak.

“Close initial densities offer high probabilities of producing high-quality timber,” the authors claim, but state that “wider spacing has been regarded as an opportunity to save money in recent years” which is an implicit criticism of the current Irish practice of planting 3,300 plants/ha supported by the Forest Service. This should have been backed up by a strong editorial stance as many foresters believe that a stocking rate of 3,300 is adequate. The authors make no reference to the much lower planting density of 1,400 plants/ha advocated by Jean Lemaire in his book Oak: fine timber in 100 years, translated by Bede Howell (Table 1).

These quibbles aside, Broadleaf Forestry in Ireland is without doubt the definitive work on the subject as the scope is wide, catering for all aspects of what is a complex subject in terms of time, silviculture and eventual markets.

The authors cannot be accused of underestimating the expertise and knowledge required in successfully managing broadleaves. Compared with conifers, broadleaves demand intensive management by foresters and growers, greater soil and site analysis as well as in-depth knowledge and expertise by the eventual users, including timber processors, manufacturers, designers, architects and other specifiers.

The economic, social and environmental challenges associated with broadleaf forestry are covered well by Huss et al but, in the final analysis, “planters of broadleaf trees have to be people with a vision for the future,” they maintain. “How else” they understandably ask “can one explain the undertaking of an enterprise from which the planter will rarely receive a dividend?”

Broadleaf Forestry in Ireland by Jürgen Huss, Padraic Joyce, Richard MacCarthy and John Fennessy, (hardback 496 pages) and published by COFORD is available on request from the Department of Agriculture, Food and Marine, priced €55, including postage (contactorla.cashen@agriculture.gov.ie).

The harvesting of hurley butts started in early September in the Centenary Forest, Teagasc, Johnstown Castle, Co Wexford. This is a collaborative project by the GAA Ash Society, Teagasc, Forest Service, Coillte and The Irish Guild of Ash Hurley Makers (IGAHM). Its goals are to help ash growers to fully optimise their forests, to create a culture of forest management, to support the ash hurley-making industry and to develop initiatives aimed at addressing the challenges of pests and diseases such as ash dieback.

The ash was planted in 1984 as part of the GAA centenary celebrations. Since then, the forest has been used as a research trial and has generated valuable information in relation to many aspects of growing ash including spacing, nutrient management, weed control and thinning.

Speaking at the launch, Professor Gerry Boyle, director of Teagasc, acknowledged the foresight that both Dr Noel Culleton (formerly of Teagasc) and the GAA demonstrated in establishing ash research trials, which “have greatly contributed to knowledge transfer on the establishment and management of ash in Ireland”. The Forest Service estimates that there are almost 19,000ha of ash woodland in the Republic of Ireland. “The Department has recently provided €350,000 in research funding towards breeding for resistance and also provide grant aid for the tending and thinning of ash sites,” said a Forest Service spokesperson.

Confirmed findings of ash dieback continued to increase over 2016. Confined to ash, the disease is caused by the fungal pathogen Hymenoscyphus fraxineus, previously known as Chalara fraxinea. The emphasis now is on scientific research of the disease both in Ireland and elsewhere in Europe, with a focus on developing ash tree breeding programmes. “These will aim to develop trees showing strong tolerance to the disease, which is a key component in the strategy to combat the disease in the long-term,” said a Department spokesperson.

Minister Andrew Doyle visited Donishall Nursery, Co Wicklow, recently to discuss the planting programme with None-so-Hardy Nurseries (NSH) staff.

Up until recently, the nursery supplied virtually all plants for afforestation but “there has been a significant shift to reforestation sites in recent years which require larger plants to compete against pine weevil attack,” said John McCarthy, NSH.

“The funding allocated in Budget 2017 will allow for over 7,100ha of new forests to be planted, almost 800ha more than the total area planted in 2015,” said Minister Doyle.