RECOMMENDATIONS FOR BEST PRACTICE

Transcription

1 PRODUCED BY THE COMMITTEE ON PLANT SUPPLY AND ESTABLISHMENT SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING RECOMMENDATIONS FOR BEST PRACTICE ON BEHALF OF THE JOINT COUNCIL FOR LANDSCAPE INDUSTRIES

2 ACKNOWLEDGEMENTS This guidance note to best practice has been prepared by the Committee on Plant Supply & Establishment on behalf of the Joint Council for Landscape Industries (JCLI) as part of its role in promoting good practice in the Landscape Industries. Considerable thanks are due to Mr John Aldhous, a fellow of the Institute of Chartered Foresters, who wrote and co-ordinated the work. The permission of the Forestry Commission to reproduce Figures 1 and 2 is gratefully acknowledged. Published by the Landscape Institute on behalf of the Joint Council for Landscape Industries which comprises: ➊The Arboricultural Association (AA) ➊The British Association of Landscape Industries (BALI) ➊The Horticultural Trades Association (HTA) ➊The Institute of Leisure and Amenity Management (ILAM) ➊The Landscape Institute (LI) ➊The National Farmers Union (NFU). CONTENTS Specifying seed sources for trees 2 Importance of seed origin 2 Terms relating to seed sources for amenity and forestry planting 3 Botanical descriptors 4 Geographical descriptors 4 Origin and provenance of seed for forestry 5 Amenity plants raised from seed 5 Local seed zones and Regions of Provenance 5 Historical descriptors 7 Ecological descriptors of seed sources - woodland types 8 Qualitative descriptors for forest seed sources 8 Matching seed origin and provenance to site when planting trees 9 Uncertainty about origin of native species 10 Special local trees 11 Record of provenance and verification 11 1st Edition: Published February 2002 The JCLI

3 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 1 INTRODUCTION The United Kingdom has a long history of successful introductions of plants, at first from Europe and later from other temperate regions across the world. These have contributed hugely, not only as economic crops to the rural economy, but also as amenity plants to the beauty of town and country landscapes. In recent years, there has been a resurgence of interest in native woodland trees and shrubs to restore, as far as this is possible, native woodland habitat. This has led to new demands for plants from a wider range of seed sources, and in particular, from local sources. The description of sources of seed for such plants has not always been well defined and for that reason has led to misunderstandings. Publication of guidance now on recommended terminology for sources of tree seed has been stimulated by two factors. Firstly, EC Directives affecting trees have recently been substantially changed. Secondly, the Horticultural Trades Association have developed a National Plant Specification (HTA see list of references at end of paper) and a Nursery Certification Scheme covering similar ground, particularly for amenity species. When the UK first joined the European Community, it acquired an obligation under EC Directives to promote use of the best available seed sources when planting for forestry purposes. ( Forestry purposes in practice has included all planting under the Forestry Commission Woodland Grant Schemes and similar schemes.) A revised, consolidated Directive was published in It is expected to be implemented in the UK through a revision of the Forest Reproductive Material Regulations (FRM Regs) to come into effect in 2003 (Forestry Commission 2001). The HTA National Plant Specification (NPS) describes woody and herbaceous plant species that may be used in amenity and landscape plantings. While many species listed in the NPS are propagated vegetatively, a significant number are raised from seed. The recommendations that follow are compatible with the new EC Directive and with those sections of the National Plant Specification relating to trees raised from seed for large-scale planting.

4 2 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE SPECIFYING SEED SOURCES FOR TREES People who specify trees and shrubs for forestry and large-scale amenity planting rarely grow the stock to be used. They rely on being able to purchase from commercial nurserymen, plants raised from seed that will meet their requirements. Whatever the motivation for planting, for native and non-native tree species, selection of the appropriate seed source may make the difference between long-term success and failure. Descriptions of seed sources must therefore be unambiguous whenever seed is sold or plant supplies are being negotiated between specifier and nurseryman. Seed source is not relevant where vegetatively propagated varieties are used in planting schemes. IMPORTANCE OF SEED ORIGIN Most British native trees and shrubs have a widespread distribution through northern and central Europe. Many introductions from the nearer parts of continental Europe survive and grow well. However, introductions from eastern and central Europe are commonly less vigorous than native sources and often show differences in dates of bud-break, flowering, onset of winter dormancy etc, when introduced here (Worrell 1992, Samuel 1997). Certain origins of species introduced to Britain over the last 200 years are susceptible to disease, debility or even premature death. Choice of seed origin by species (Lines 1992) gives guidance for many of the introduced timberproducing species. Independently of the EC, the World forestry conference at Rio in 1993 drew attention to the destruction of natural forest habitat, especially in tropical and subtropical regions, and sought to conserve habitats with particularly rich or rare fauna and flora. It also provided a stimulus to heavily populated and industrialised countries to review the remnants of their own natural woodlands, and take steps to protect any species, important seed origins or woodland types that were at risk. Agenda 21 is an outcome of the Rio conference. In the UK, there has been widespread popular support for attempts to protect, restore and extend the area of native woodland and to favour native species of

5 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 3 local origin. The very limited extent even of semi-natural native woodland in Britain is, however, not fully appreciated. TERMS RELATING TO SEED SOURCES FOR AMENITY AND FORESTRY PLANTING STOCK Everyday usage to describe seed sources has not been consistent in the past, partly because of the number of terms in use. Table 1 (below) lists 30 descriptors of seed sources for forestry and amenity planting stock. These are grouped as botanical, geographical, historical or ecological descriptors, according to their function and frequency of use. They are all attributes of seed sources. The table is followed by definitions and comments on their use in specifications and descriptions of planting material. These terms and definitions are recommended for general use in the forestry and landscape industries, in particular, in the use of origin, provenance and local. Table 1: Descriptors of seed sources for forestry and amenity planting stock Class of descriptor Frequency of use for forestry and amenity planting stock Commonly Sometimes Rarely Botanical Genus, species, cultivar, common name Clone, variety, hybrid Subspecies, forma Geographical Provenance, origin, source, stand, local seed zone, region of provenance Historical/ geographical Native, alien, exotic, introduced, naturalised Natural range, indigenous Autochthonous, extended range Ecological National vegetation classification, woodland type Forest type Qualitative Selected, sourceidentified, qualified (see also tested )

6 4 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE A seed source is a stand or more dispersed population of trees or shrubs, the location of which can be described and mapped, and within which seed is collected. Sources are necessarily of seed-bearing age but are not necessarily uniform in age. Forestry seed collections are recommended to be made from not less than 30 healthy trees, taking similar quantities of fruits or cones from each, thereby setting a lower limit on the size of the seed source. Large collections could come from a source area several square miles in extent. A seed stand is a mappable population of trees which is fairly uniform in composition. Under the new EC Directive, firms collecting and marketing UK seed of EC listed species will have to be registered through the Forestry Commission, whether seed is being sold for forestry or for amenity purposes. BOTANICAL DESCRIPTORS The botanical descriptors listed should be used as defined in the Horticultural Trades Association National Plant Specification (HTA 2002). The botanical name (genus and species) should always be specified; also any relevant variety, cultivar or other name. GEOGRAPHICAL DESCRIPTORS These may be important guides to the relative long-term performance of plants whenever a range of sources of seed is available commercially. See Importance of seed origin on page 2. Origin and provenance of seed for forestry The EC Directive and FRM regulations include definitions of provenance and origin for plants marketed for forestry purposes (SI 1977/891) (FC 1987). In Britain, these have been applied to all commercial forestry stock since the 1970s. While the regulations are currently under revision, the definitions are unlikely to differ significantly from the following: Seed provenance the geographic locality of the trees from which the seed in question was collected. Seed origin the geographical locality within the natural range of a species from which seeds or plants were originally introduced.

7 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 5 For any seed lot, information on provenance should always be available. The origin of trees that have been planted may often not be known with certainty. Examples of use of these terms i Pinus sylvestris seed collected from a native stand in Glen Tanar would be of Glen Tanar origin and Glen Tanar provenance; ii Fagus sylvatica seed collected in Cirencester Park, Gloucestershire, in plantations known to have been planted with seed originating from the Forêt de Soignes in Belgium would be of Belgian origin and Cirencester Park provenance; iii Quercus robur acorns collected in Hampshire in an oak plantation of unknown origin would be of Hampshire provenance, origin unknown. Amenity plants raised from seed Origin and provenance are defined for amenity planting in the HTA National Plant Specification, Section T10.2. These definitions are repeated in sections covering shrubs and herbaceous species raised from seed. While the exact wording differs, the meanings of the definitions of origin and provenance in the NPS and in the EC Directives, old and new, are the same. Amenity plants Country of origin The NPS in Section T10.2, includes a British Standards definition of Country of origin as the country where plants have been growing in the latter half of the most recent growing season. This definition may be relevant to vegetatively propagated ornamental cultivars but must not be applied to forestry stock raised from seed. Local seed zones and regions of provenance Seed sources from adjoining areas with similar site and climate can be grouped together as coming from a local seed zone. The size of any such grouping may vary by locality. Local seed zones may in turn be grouped together to form Regions of Provenance. Figure 1 (overleaf) shows a Forestry Commission map of Local seed zones and Regions of provenance for native trees and shrubs in Britain (Herbert et al 1999). The four Regions of Provenance are differentiated on the basis of accumulated summer heat and total annual rainfall. They have been divided into 24 local seed zones, using ecological and natural physical boundaries. These are the zones and regions recommended when specifying origins of most native species for forestry purposes.

8 6 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE Figure 2 shows a map of seed zones for Scots pine (Pinus sylvestris) in its native range and is based on analysis of needle resins (Forrest 1980).

9 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 7 Seed from any seed source should be suitable for sites of similar soil and climate elsewhere in the same local seed zone. If seed is not available from within a preferred local seed zone, the next choice should be from among stands of good form and vigour growing at similar elevations in the same Region of Provenance. HISTORICAL DESCRIPTORS Historical descriptors are important in Britain because of the scale on which native vegetation has been destroyed and species have been moved, being planted often many hundreds of miles from their original seed source. The terms authochthonous, indigenous, native, alien and naturalised may each be used to describe an aspect of the history of the seed source. The term autochthonous is likely to be unfamiliar to plant users but is incorporated in the revised EC FRM directive. An autochthonous (synonym site-native) seed source is one which has been continuously regenerated naturally. However, a seed source may also be considered autochthonous if regenerated artificially from seed collected from the same source or from autochthonous stands in the near vicinity (EC 2000). An indigenous seed source is an autochthonous seed source, or is a source raised from seed, the origin of which is in the same region of provenance (EC 2000). The range of a species is the geographical area over which a species occurs (or occurred before clearance by man). Natural range is that part of the range where the species occurs/occurred naturally, without intervention by man. A species is native within that range. A species natural range may change in response to a natural change in climate; it is dynamic, not static. Extended range is the additional area where a species occurs as a result of introduction by man, whether deliberate or inadvertent. A species is introduced (synonyms alien, exotic) within its extended range. If an introduced species is able to grow, reproduce and colonise, it is naturalised. A species such as Fagus sylvatica (beech) which, in Britain, occurred naturally only in central and southern England, is native there and introduced/ naturalised elsewhere.

10 8 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE ECOLOGICAL DESCRIPTORS OF SEED SOURCES WOODLAND TYPES Woodland and forest form the natural vegetation cover of temperate and tropical land wherever there is adequate rainfall and depth of drained soil. On a large scale, natural woodland commonly forms a mosaic of woodland or forest types of different ages. The component woodlands reflect the physical environment (soils, climate etc), history of natural colonisation and history of natural disturbance (fires, storm damage etc). Woodland types are commonly defined by the assemblage of dominant species. Where a substantial cover of temperate forest cover remains (eg parts of Europe, N. America), forest types have been described and used as a basis for zoning seed supply. In Britain, work on a National Vegetation Classification (NVC) started in 1975 and led to publication of British Plant Communities Vol 1 Woodlands and Scrub (Rodwell et al 1991). In this, 25 main woodland types are described in the context of their soils and climate. Locations of examples of each community are given but these are too few to form the basis for any seed zonation. QUALITATIVE DESCRIPTORS FOR FOREST SEED SOURCES Both the original and the revised EC FRM Directives promote the concept that, within forests, trees in some localities show better form and/or vigour than in others and that this better performance is repeated their progeny. If such better stands are registered as available for seed collection, they are categorised as selected. Considerable effort has gone into identifying selected stands. The original directive required that selected seed be used for forestry purposes, special permission being required for collections from sources that did not meet the criteria for selected seed sources. The revised FRM Directive has retained the selected category, but allows collections from non-selected seed sources to be made without special permission, such collections being categorised as source-identified. Provenance and origin descriptors apply to source-identified and selected sources.

11 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 9 In Britain, long-term tree improvement programmes have led to the creation of seed orchards and collections of progeny-tested parent trees of the most important commercial conifer species. Trees raised from seed from such tested progeny grow appreciably faster than stock from unimproved seed. Improved seed is available for Sitka spruce (Picea sitchensis) and Scots pine (P. sylvestris), and on a small scale, hybrid larch (Larix x eurolepis). Such seed is given the new FRM quality categorisation qualified. Each seed orchard is registered, its name constituting its provenance. Poplar clones which have been subject to intensive screening for disease resistance, and which have been released for forestry use are categorised under the EC FRM Directive as tested. Such clones are all vegetatively propagated cultivars and as such, neither seed provenance nor seed origin is relevant. The Directive requires that whenever plants covered by the directive are marketed for forestry purposes, the relevant quality category be stated (EC 2000). MATCHING SEED ORIGIN AND SEED PROVENANCE TO SITE WHEN PLANTING TREES Table 2 (page 10) gives some indications of priorities when seeking seed for amenity and forestry planting schemes. When maintaining or re-creating native woodland and woodland habitats by planting stock raised from seed, knowledge of origin is essential and important. First choice is plants from origins within the same local seed zone, in preference to origins from farther afield. Plants of unknown origin should not be planted in such schemes without good reason. For the bulk of general woodland planting, suitable seed origins of native species should be sought within the local Region of Provenance. For non-native species, origin may be important, but, being introduced, origins that are local within the UK are not possible. For European larch, lodgepole pine and Douglas fir, selection of suitable origins remains essential. For other introduced species with a considerable altitudinal range in mountainous terrain, origins from low elevations may possess morphological or phenological characteristics that differ markedly from those of origins of the same species from high elevations in the same region. Seed should be sought from seed zones with climates most nearly matching those of the planting site (Lines 1992).

12 10 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE Table 2: Matching seed source to site for amenity and forest planting Seed source Restoration of ASNW # Native woodland fragments General woodland planting Land restoration Open planting Urban landscape Local seed zone **** *** ** * Local Region of provenance *** **** **** *** Source in Britain ** ** ** ** Near- European origin x */** */** */** Other origin x Use dependent on origin and circumstances of site **** *** ** * Decreasing order of preference # Ancient semi-natural woodland Where local seed sources are essential, sufficient time may have to be allowed for stock to be raised under a contract grow or similar arrangement Alternatives that may be appropriate for C and SE England For other planting, especially amenity planting in parkland or similar open landscapes, knowledge that plants of native species are of local provenance is a reassurance that plants have grown successfully in the locality in the past. Nevertheless, for many amenity and landscape sites, there has been so much interference with the site and environment that sourcing from vigorous healthy stands within the local Region of provenance is likely to be as suitable as any more local source. Uncertainty about origin of native species Because of the scale of woodland clearance in Britain and the long period over which British woodlands have been managed for specific products, records of the origin of planting stock of native species have often been lost. While formal records of any given current seed collection may show the origin as not known, any supplementary information indicating the probability that a provenance is of local origin may be valued by prospective purchasers.

13 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE 11 Because of lack of certainty about origin and hence lack of supplies of known origin, specifiers of native species may have to accept local provenance as a substitute for local origin. Special local trees Seed collections from culturally special local trees will carry with them the sense of the special association. They carry no guarantee that the stock raised will reproduce particular characteristics nor have any special merit in terms of nativeness, localness of origin or naturalness unless these can additionally be demonstrated. Record of provenance and verification Because seed from any given collection is likely to be used within a relatively short time, it should always be possible to find out the provenance of that seed and obtain independent verification. Future forest plantings in Britain are likely to come within the scope of the UK Woodland Assurance Scheme. This sets standards for environmental aspects of silviculture; timber produced in approved woodlands may be so certified. It is possible that certification or similar assurance of the provenance of a seed source will be insisted on for new grant-aided plantings and that available information on origin will be considered desirable.

14 12 SPECIFYING SEED SOURCES FOR TREES FOR LARGE SCALE AMENITY AND FORESTRY PLANTING: RECOMMENDATIONS FOR BEST PRACTICE REFERENCES Aldhous, J.R Relevance of local provenance to amenity and forest tree planting. Quarterly Journal of Forestry 95 (1) EC 2000 Council Directive 1999/105/EC of 22 Dec on the marketing of forest reproductive material. Official Journal of the European Communities L 11 Vol January, Forestry Commission 1987 The Forest Reproductive Material Regulations, 1977 An explanatory booklet. Forestry Commission, Edinburgh. Forestry Commission 2001 Consultation paper on the new EC Directive on the marketing of Forest Reproductive Material. Forestry Commission Country Services, Edinburgh. 20 pp. Forrest, G.I Genotypic variation among native Scots pine in Scotland, based on monoterpene analysis. Forestry Herbert, R., Samuel, S. & Patterson, G Using local stock for planting native trees & shrubs. Forestry Commission Practice Note 8 Forestry Commission, Edinburgh. HTA 2002 National Plant Specification. Horticultural Trades Association, Theale, Reading, Berks. Lines, R.L Choice of seed origin by species. (in) Seed manual for forest trees. Forestry Commission Bulletin HMSO London. Rodwell, J.S. et al 1991 British Plant Communities Vol 1 Woodlands and Scrub Cambridge University Press. Samuel, C.J.A Growth characteristics of locally grown native provenances compared with translocated and foreign stock. Proc. discussion meeting, Native and non-native in British forestry 1995, at University of Warwick Institute of Chartered Foresters, Edinburgh. Worrell, R A comparison between European, continental & British provenances of some British native trees. Forestry 65 (3)

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