BIHT

Sweet chestnut is thought to have been introduced by the Romans from southern Europe and has been grown in the UK for some 2,000 years: extant ancient trees include the Tortworth chestnut in Gloucestershire, reputed to be over 1,000 years old. The main chestnut area of 18,000 ha is concentrated in England, especially in the southern counties of Kent and Sussex, where there are extensive stands of commercial coppice, often grown with oak standards (see photo below). In the UK, chestnut is grown solely for its timber as nut production is not currently economically viable under UK growing conditions. It is presently a minor species in Irish forestry, but nevertheless appears on 191 sub-compartment records in the Republic. Although very much a lowland species here, recent research findings have shown that when grown in a matrix of suitable nurse species, its planting range can be extended to moderately exposed sites.

Good quality coppice, Kent

Sweet chestnut is usually considered an ‘honorary native’ in southern England: it has a reasonable claim to be able to maintain levels of wildlife biodiversity similar to that of native broadleaved woodland. The timber is naturally durable, with few sapwood rings, and requires no preservatives for outdoor use. Mature standard trees are highly valued for their timber: their suitability for furniture and for other purposes is similar to that of oak. However, large diameter stems of chestnut can be susceptible to timber defects, especially ring shake and spiral grain. Fortunately, with the advancement of saw technology, together with modern wet gluing technology, beams can now be manufactured for the structural utilisation of small diameter chestnut timber.

Climate change and declining markets, together with biotic factors (such as the fungal diseases Phytophthora spp (causing ‘ink’ disease) and Cryphonectria spp (causing Chestnut blight, not yet present in the UK)) pose potential threats to the species across Europe. Geographic differentiation between populations in Europe is reflected by variation in adaptive traits such as budburst, bud set or growth rate: populations from wetter and cooler areas have a greater heat requirement for budburst, grow faster and cease growth later than those found in drier conditions. Studies using molecular markers indicate that the level of genetic diversity in British populations is high and comparable to continental levels - suggesting that in the past there have been multiple introductions from different sources.

Current research

The BIHIP Sweet Chestnut Group was formed in June, 1999 with the objective of developing a programme to improve the quality of trees in Britain and Ireland, while at the same time conserving genetic variety. This integrated approach is designed to improve timber yield and marketability as well as providing insurance against future threats from disease, pests and climatic uncertainty. The Group’s four main objectives are as follows:

1. To identify, conserve and utilise key genetic resources (seed stands and outstanding trees) for the improvement chestnut in Britain and Ireland;

2. To increase the quality, quantity and utility of the timber and coppice produced per hectare through genetic and silvicultural studies;

3. To improve industry and public awareness and support of chestnut by promoting its merits and uses;

4. To provide industry with supplies of high quality seed and seedlings from selected seed stands, and clonal seed orchards comprising of superior, ecologically adapted individuals.

Longer term objectives are to research a number of themes:

• variation in adaptive traits (e.g. seed production and periodicity, frost avoidance, drought tolerance, etc.) in relation to regional differences and climatic change scenarios;

• genetic variation within British and Irish chestnut populations;

• characterisation of flowering types and frequency in plus trees;

• adaptation to silvicultural practices of plant material from different sources, e.g. in coppice, singled and maiden stands;

• factors affecting the economic value of chestnut wood;

• causes of timber defect, such as ring shake, and factors affecting wood quality and utilisation;

• ecological impacts of commercial chestnut stands in both existing semi-natural woodlands, and newly planted areas.

Seed stands and breeding seedling orchards

Traditionally, registered seed stands have been the source of improved chestnut seedlings in England (although not in Ireland, where the summers are rarely warm enough to fully ripen the seed). There are currently four in England and three in Ireland, the latter established recently following a Group search initiative. In Britain seed stands are recorded on the National Register, managed by Forest Research. Registration is free. Seed merchants and nurserymen use this register to obtain better quality seed and will pay a premium for it. We are always looking for new high quality stands welcome suggestions from readers.

In the spring of 2002 a breeding seedling orchard was established on the Somerset Levels at Broadmead Farm, part of the Maunsel Estate, using the progenies of eighteen phenotypically superior Plus Trees (see Fig. 1) identified by members of the Group.

Potential Plus Tree, Gloucester, November 2005

This 1 ha site is a former fruit orchard on fen peat soil. The 1,000 surviving trees are periodically assessed for survival, height growth and phenological traits. Over time, the orchard will be selectively thinned to ensure that only the best performing individuals remain for seed production. Under the Forest Reproductive Material Regulations, the orchard can be registered as tested.

Clonal seed orchards

While seed stands and breeding seedling orchards are a valuable resource for further breeding development, the creation of clonal orchards is the Group’s main priority. This involves taking cuttings from selected Plus Trees which are grafted on to rootstocks before transplanting them to the orchard site. The aim is to collect clonal material from 50 Irish and 100 British Plus Trees, including selections from both coppice and maiden stands. This emphasis on clonal selection has several advantages: the identity and quality of the genotype of the plus tree is known and thus preserved; the trees originate from a wide range of sites, ensuring broad genetic diversity; the problem of collecting seed in lean fruiting years is avoided; and earlier seed production will be achieved. To date vegetative shoots have been collected from 58 British candidate plus trees which have been grafted on to rootstocks and held in a collection at East Malling Research. Of these, material from 29 individuals has been despatched to Ireland where a duplicate collection is currently being established. The Group has also made significant progress towards procuring Irish material, with 32 plus trees identified in 2006 and a further 24 in 2007, bringing the Irish total to 56.

The location and collection of at least 50 more British plus trees is the current focus of a campaign to encourage landowners to donate further material to the collection (see below). The eventual aim is to establish two clonal seed orchards containing both British and Irish material in England (Regions of Provenance 30 and 40), matched with two others in Ireland. In addition, sites will be sought to establish four national clonal trials, representing 100-150 plus trees selected from a wide geographical range.

Current programme

In recent years the Group has received generous support from Woodland Heritage and other bodies in its efforts to locate chestnut plus trees for clonal propagation. Funded objectives to date include:

• promoting and advertising the case for propagating superior sweet chestnut individuals to the forestry profession, timber growers and landowners;

• consolidating, at two locations in Britain and Ireland, the present small collection of plus trees as a clonal hedgerow, prior to setting up clonal seed orchards and provenance trials;

• identifying Irish plus trees and to obtaining scion material for propagation.

Further funds are now being sought to identify, collect and propagate the remaining British plus trees needed to make up the target total of 100 individuals. Securing the future of the present collection of propagated material at permanent sites in Britain and Ireland is another priority, as is the procurement and preparation of land for clonal orchards.

Related research

1. The CASCADE (European Union Fifth Framework) research programme – Securing gene conservation, adaptive and breeding potential of a model multipurpose tree species (Castanea sativa) in a changing environment. Within the CASCADE consortium of eleven different partner institutions in six countries, East Malling Research (formerly HRI), Kent, used molecular markers (microsatellites) to assess genetic diversity and gene flow in sweet chestnut populations across Europe (Spain, Italy, France, Greece and the UK). Six UK coppice populations were also assessed and screened for resistance to Ink disease. Further details can be obtained from http://soi.cnr.it/~chestnut or from Karen Russell at the address

2. Factors determining shake in sweet chestnut. A project at Imperial College, Wye campus, has investigated shake incidence at five contrasting sites in Kent. Site type, wood anatomy, phenology and meteorological history were examined, with clonal material collected from felled trees for physiological testing with funding provided by Woodland Heritage. The first article was published in Forestry in 2005 (volume 78, 175-186).

3. A joint Timber Trade, Forestry Commission and South East England Local Authorities initiative commissioned research project at the Building Research Establishment (BRE) to develop grading and structural standards for the use of chestnut for construction. This resulted in a British Standard for chestnut timber being established: BS 5756:1997 Specification for visual strength grading of hardwood. The mechanical data will be published as a revision to BS 5268: 1996 Part 2, Structural use of timber.

4. The results of the European COST G4 action 'Multidisciplinary Chestnut Research' in which the UK participated are published in Forest Snow and Landscape Research, 2001, Volume 76, issue 3: 327 - 517: 'Castanea sativa: pathology, genetic resources, ecology, and management'. U. Heiniger, Ed. See: http://www.wsl.ch/lm/publications/archiv/contentsV76_2-en.ehtml.

5. A review of The ecological impact of sweet chestnut coppice silviculture on former ancient, broadleaved woodland sites in south-east England by Imperial College was published as English Nature Research Report 627 (2004), obtainable form English Nature, Peterborough.

Figure 1: Characteristic of an ideal ‘plus’ tree of chestnut

Adapted to local climate and clearly superior as a timber tree to neighbouring trees Pest and disease free Good growth, healthy foliage Straight, circular stem with absence of spiral grain, fluting and buttressing Strong, well balanced crown with good apical dominance/persistent leader Uniform and lightly fissured bark with absence of long fissures Absence of epicormic shoots Fine branches Horizontal branches Desirable wood properties

Group membership

The sweet chestnut group currently has 12 members:

• Geraint Richards (Chairman), Duchy of Cornwall, Liskeard, Cornwall

• Karen Russell (Secretary), Lockhart Garrat

• Bill Blight, forestry consultant, Crediton, Devon

• Alan Betts, Forestry Commission, Alice Holt, Farnham

• John Baly, Woodland Improvement and Conservation Ltd., Huntley, Glos.

• Will Bullough, Whitney Sawmill and workshops, Herefordshire

• Robert Guest, Forestry Commission, Coleford, Glos.

• Ted Horgan, Coillte Teoranta, Mallow, Ireland

• Robert Lee, Forestart Ltd., Shrewsbury, Shropshire

• Peter Buckley, Consultant

• John Leigh Pemberton

• Edward Stenhouse, Inwood Developments, East Sussex

To contact any of the Group Members please contact the Sweet Chestnut Group secretary Karen Russell ().

Acknowledgements: The Group gratefully acknowledges funding and support from Woodland Heritage, COFORD, Coillte Teoranta, the European Union, DEFRA, Forestry Commission and Kent County Council, all of whom have contributed towards the projects outlined above.