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- Herausgeber: Crowood
- Kategorie: Fachliteratur
- Sprache: Englisch
Now in full colour, this is the second edition of this highly acclaimed book. Woodland Management is essential reading for anyone with an interest in trees and woodlands, whether they simply enjoy walking in the woods, are considering buying woodland, or wish to gain a greater understanding of the history and management of Britain's woodland. The book begins with a look at how our woodlands have developed and a discussion of the different types of woodland, and then explores, in a non-technical way, all aspects of management. It considers: broadleaf and conifer woodlands; factors influencing the choice of tree species; surveying and mapping; the seasonal cycle and the operations that occur at different times of the year; conservation and biodiversity; planting new woodland; natural regeneration; coppicing; the types of site; ground preparation; protecting ancient trees; growing trees for timber; thinning and felling; methods of selling timber; generating revenue from timber production and other sources; the factors involved in buying and owning woodlands; where to find grants; how to write a management plan; who to contact for further information; and much more. An indispensable guide for all those interested in maintaining our rich woodland heritage. Now in full colour, this is the second edition of this highly acclaimed book, which is illustrated with 86 colour photographs and 37 diagrams.
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Veröffentlichungsjahr: 2013
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First published in 2005 by The Crowood Press Ltd Ramsbury, Marlborough Wiltshire SN8 2HR
www.crowood.com
This e-book first published in 2013Second edition 2013
© Chris Starr 2005 and 2013
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publishers.
British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.
ISBN 978 1 84797 618 5
Dedication To Hannah and Becky.
‘We all travel the Milky Way together, trees and men.’ John Muir, The Mountains of California
Disclaimer Chainsaws and all other tools and equipment used in woodland management should be used in strict accordance with both the current health and safety regulations and the manufacturer's instructions. The author and the publisher do not accept any responsibility in any manner whatsoever for any error or omission, or any loss, damage, injury, adverse outcome, or liability of any kind incurred as a result of the use of any of the information contained in this book, or reliance upon it. If in doubt about any area of woodland management readers are advised to seek professional advice.
All photographs by the author, except where indicated otherwise. Line-drawings by Keith Field.
Contents
Acknowledgements
Introduction
Chapter 1 Woodlands: Past, Present and Future
Chapter 2 Getting to Know Trees and Woodlands
Chapter 3 The Broadleaves
Chapter 4 The Conifers
Chapter 5 AVision for the Woodland
Chapter 6 Getting to Know Your Woodland
Chapter 7 Biodiversity Matters
Chapter 8 Regenerating and Creating Woodland
Chapter 9 The Seasonal Cycle and Woodland Maintenance
Chapter 10 Silviculture and Stewardship
Chapter 11 Generating an Income from Woodland
Chapter 12 Buying and Owning a Woodland
Glossary
Further Reading
Useful Addresses
Index
Metric/Imperial Conversion Factors
Acknowledgements
This book could not have been completed without the help of family, friends and colleagues, and although I did not always heed their advice and thoughtful criticism I am very grateful for it.
I should like to take this opportunity to thank the following owners who kindly allowed me to use their woodlands as case studies. Toby Coke at Weasenham New Wood, Jim Ralph at Knapp Coppice, Maggie Gordon and Bob Lee at Barfil Farm, and Graham and Sarah Chaplin-Bryce at Low Bridge End Farm, generously gave me their support and encouragement. I hope the case studies manage to do justice to their hard work and vision.
I am grateful to those who kindly let me use their photographs, woodland sites and drawings, including Ted Wilson, Hans Morsbach, Jim Ralph, Chris Seymour, Edward Mills, Rebecca Oaks, Neville Elstone, Tom Kent, Nigel Williams, Martin Clark, Colin Blanchard and Malcolm Riding. Simon and Jacqueline Stone at Robin Forest Surveys and John O’Keefe at the Harvard Forest were very helpful in responding to my last-minute pleas for material.
Bob Watson, Mike Jones, Ted Wilson, Eva Casson-du-Mont and Dorothy Parry commented on various drafts of the text while my employers, the University of Central Lancashire, funded my sabbatical leave. The staff at The Crowood Press always responded quickly to my requests for help and advice, and Keith Field has done a great job of turning rough sketches into excellent diagrams.
Finally to my parents, Audrey and Richard, for supporting me in my choice of career, and to my wife Helen, who kept me fed and watered in the shed and occasionally steered visitors away as the manuscript deadline approached – thank you!
Introduction
I have read many definitions of what is a conservationist, and written not a few myself, but I suspect that the best one is written not with a pen, but with an axe. A conservationist is one who is humbly aware that with each stroke he is writing his signature on the face of his land. Signatures of course differ, whether written with an axe or pen, and this is as it should be.
Aldo Leopold A Sand County Almanac, 1949
While writing this book I spoke to many woodland owners, and the more I talked to them the more I came to realize the diversity of reasons that people have for owning, buying or wishing to buy woodland. This has meant that I have, of necessity, had to cover a very wide range of material and had to think about this from the perspective of those who often know little or nothing about woodland history, silviculture or wildlife management. This is more of a problem in Britain than in many European countries, since Britain lost much of its rich woodland culture when the rural population moved to the cities during the industrial revolution. Perhaps the increasing interest we see in woodland today is part of a migration back to the countryside, at least in spirit, and a reawakening of a long-dormant woodland culture, once so rich here and evident in our woodland heritage.
Increasingly, woodlands are being purchased by individuals seeking a stronger link with their natural heritage. Others buy woodland for a wide range of objectives including, among many others, financial return, investment, sporting and recreation, lifestyle change, and habitat and wildlife conservation. Some acquire it simply for its own sake – because it is a pleasure to own. For those not in a position to actually own a woodland, membership of charities concerned with the conservation of Britain’s woodland heritage enables people to make a contribution through voluntary work.
Woodlands are not static, and their extent, composition and structures have changed considerably over time. They are surprisingly resilient and, although many have been cleared to make way for farming and urban development, others have survived and continue to provide a strong link with the past. Where land is left idle, woodlands return with great vigour to reclaim the space, often forming complex and interesting new habitats. Even in hostile urban environments, woodlands flourish on the most degraded sites, improving the soils and microclimate.
The terms ‘woodland’ and ‘forest’ can have different meanings. In the past, the distinctions that existed were based upon land ownership and use; more recently forests have come to be seen as places for timber production. However, the New Forest in Hampshire, itself a woodland set aside originally as a royal hunting reserve and later extended through planting, has recently been designated a national park with protected status. Suffice it to say that such distinctions, while of interest to historians and academics, are not central to the purpose of this book. Woodland is used throughout this book as a general term to mean land covered with trees and managed for a wide variety of objectives, but excluding large-scale commercial forests.
This heart-shaped woodland grows on the side of Blease Fell in Cumbria and was planted by a local farmer. It is seen every day by thousands of motorists travelling along the M6 near Tebay, and by rail passengers going north on the West Coast line from London to Glasgow: look out of the right-hand side window shortly after leaving Oxenholme.
There is no right way to manage woodland, but there are some wrong ways and there are some guiding principles. An understanding of how different trees res pond to such things as soil, light and competition is important if cause and effect are to be understood. The choice of a particular species might be dictated by personal preference, by the history of the site, by the end use of the timber or by the needs of a particular habitat or animal.
This is not a book for the professional forester, but rather an introductory text aimed at those with an interest in owning and caring for woodlands, whatever their particular objectives. I have tried to keep jargon to a minimum, and have used technical terms only when absolutely necessary. The common names of tree species will be used throughout, but in some cases the scientific name is also added. This is not to confuse, but to add another dimension to an understanding of trees and woodland. The scientific, or Latin, name often describes a species better than the common name, and is recognized throughout the world. In some cases, woodland types are described by their scientific names rather than by the common ones.
Although many of the technical principles and species described in this book apply equally to woodland throughout temperate Europe, the cultural, social and legislative framework of England, Scotland and Wales is sometimes woodland specific. In addition, the impact of devolution on, for example, woodland grants and policies has led to a divergence of approach between the three countries. (I was also asked to consider including Northern Ireland and the Republic of Ireland, but they, too, have quite different legislative and land-use structures and priorities, although much of the book applies equally to them.) For these reasons, the practical management of woodlands in Britain – meaning England, Scotland and Wales – is the subject of this book.
A glossary of technical terms will be found at the end of the book and, for the reader interested in finding out more, a list of sources of further information and guidance is included, together with a list of technical publications and more advanced reading.
The history of woodland management is partly one of keen amateurs and landowners experimenting with new species, approaches and techniques. Many woodlands are now in better hands than they have been for years, and the success of new initiatives bodes well for future generations. It is too easy to be despondent in the face of the great global concerns facing the natural world. Local actions in local woods may help to put these concerns into perspective, and thereby enrich local lives, local landscapes and local wildlife.
CHAPTER 1
Woodlands: Past, Present and Future
In the absence of people, Britain and, indeed, many other countries throughout the world, would be substantially covered in woodland. The highest mountains and the estuaries aside, woodland would stretch from sea level to above 600m, forming what is often referred to as ‘mixed oak forest’. In reality, this would have been a complex mosaic, consisting mainly of broad leaved species, with open spaces and, in places, grazed pasture woodland. Only in the more northerly regions and on some of the poorer soils in the south would Scots pine have flourished. The species composition of this mosaic would have varied in response to the local climate, soils and the degree of exposure. Although Britain is a small island, it exhibits a wide range of microclimates, and the woodland would have reflected this.
The Wildwood
Oliver Rackham, the eminent woodland historian, evocatively refers to our prehistoric forests as the ‘wildwood’, reflecting the diverse nature and primitive hold they have on us. We have a strong affinity with this wildwood and it is reflected in our fables, our literature and in our deepest desires and fears. It is easy to forget that not so long ago large mammals roamed our woodlands. The wild boar, wolf, beaver and elk all lived in Britain’s woodland before hunting drove them to extinction. The last wolf was killed in Scotland as recently as 1743. The only large mammals now found wild are deer. Today, the reintroduction of some of these mammals is under serious consideration, particularly in the more remote parts of Britain. A private landowner is currently considering plans to convert some 10,000 hectares of land in the Highlands of Scotland into a reserve stocked with long-extinct mammals such as the bison, wolf and lynx as part of an ecological restoration project.
Forest Types
On a broad scale, Britain lies within what is known as the deciduous summer or temperate forest. This stretches across Europe and into Asia, covering vast areas as far north as Scandinavia and as far south as the Mediterranean. Although primarily made up of broadleaved species, it also contains some conifers, particularly at higher altitudes. Across much of Europe the climate is continental, exhibiting greater extremes of temperature with warmer summers and colder winters than our own.
In Britain, by contrast, the effects of the close proximity to the sea are felt everywhere and this is why even at quite high altitudes broadleaves grow well here. Only in the far north do British woodlands merge into another large-scale forest type, the northern or boreal coniferous forest that stretches across Scandinavia and Russia; in fact, most of Siberia is conifer forest. These are the native pinewoods dominated by Scots pine, and sometimes referred to as the Caledonian Forest. Now restricted to the Highlands of Scotland, often in quite isolated groups, considerable effort is under way to regenerate these pinewoods, using local seedlings protected from the effects of grazing.
Ancient westerly ‘Atlantic’ oak woodland growing on steep-sided valley slopes at Culbone in north Somerset, bordering the Bristol Channel and Exmoor. This represents something approaching the natural woodland that would have covered parts of the region in the past. The woodland has been worked for tan bark and coppice, so oak is probably more common than it would have been. The effects of wind and salt spray cause the trees to become stunted towards the shoreline.
Native Tree Species
Native tree species are those that colonized Britain naturally after the last ice age and before the formation of the English Channel some 8,000 years ago. These native species gradually moved back from mainland Europe as the climate warmed and the ice retreated. It is possible that one or two might have survived during the ice age in isolated refugia, but we cannot be sure of this.
These native tree species – of which there are about thirty-three – are listed in Table 1. In the past, they made up the complex woodland cover of Britain and are of the utmost importance for nature conservation and the maintenance of our remaining semi-natural woodlands. Today, they are supplemented by species introduced at various stages over the last 8,000 or so years, including some that would have arrived naturally had the Channel not prevented them.
Table 1 lists the native species in the generally accepted order of arrival – the wind-pollinated pioneer species followed by those with heavier seed. As they arrived, they migrated northwards, colonizing regions where the climate and soils were suitable. Some of the later arrivals, notably beech, reached only as far as the south of Britain naturally. Note that nearly all the species are broadleaved, a clear indication of our place within the temperate forest ecosystem of the northern hemisphere.
Wood Pasture and High Forest
In recent years the Dutch ecologist Hans Vera has challenged some of our notions of what the natural forest in Britain and much of Europe would have looked like after the last ice age. Rather than being dense high forest, he proposes that some of it was more like wood pasture, with widely spaced trees browsed by larger mammals. He suggests that as the ice melted, the larger grazing mammals, including the now extinct wild ox, together with the wild cattle and the wild horse, moved into Britain ahead of the trees. These ungulates had a major effect on the spread and regeneration of the woodland, resulting in more of the light-demanding species such as oak and hazel being present (a fact observed from the pollen record).
Table 1: The native tree species of Britain
Common name
Botanical name
Notes
Common juniper
Juniperus communis
Now restricted to small isolated upland and heathland sites
Downy birch
Betula pubescens
Typical pioneer species, with local adaptations to site
Silver birch
Betula pendula
Typical pioneer species, with local adaptations to site
Aspen
Populus tremula
Scots pine
Pinus sylvestris
Once native in southern England when the climate was cooler than it is today
Bay willow
Salix pentandra
Native willows important for insects
Common alder
Alnus glutinosa
Hazel
Corylus avellana
Small-leaved lime
Tilia cordata
Bird cherry
Prunus padus
Goat willow
Salix caprea
Wych elm
Ulmus glabra
Rowan
Sorbus aucuparia
Sessile oak
Quercus petraea
Important for insects and lichens
Ash
Fraxinus excelsior
Holly
Ilex aquifolium
English oak
Quercus robur
Hawthorn
Crataegus monogyna
Crack willow
Salix fragilis
Black poplar
Populus nigra
var.
betulifolia
Quite rare. Not to be confused with the introduced hybrid black poplars
Yew
Taxus baccata
Poor for wildlife but of high cultural value
Whitebeam
Sorbus aria
Midland thorn
Crataegus laevigata
Crab apple
Malus sylvestris
Wild cherry (Gean)
Prunus avium
Strawberry tree
Arbutus unedo
White willow
Salix alba
Field maple
Acer campestre
Wild service tree
Sorbus torminalis
Large-leaved lime
Tilia platyphyllos
Beech
Fagus sylvatica
Hornbeam
Carpinus betulus
Box
Buxus sempervirens
Restricted to southern England, this was the last tree to cross from Europe before the English Channel formed
The woodlands that developed did so with more open pasture woodlands forming a mosaic of grazed grassland and scrub, and areas of more closed woodland composed primarily of light-demanding species. In many ways, these would have looked much like parkland. These wooded pastures, which have been well documented in England for over 1,000 years, would have been rich in a range of different habitats including deadwood, natural pollards and grassland.
Research is currently under way to assess the sorts of grazing regimes, animal density and tree responses to grazing under conditions likely to have been found in the past. While we are still unsure of quite what the wildwood would have looked like, and the variations that might have occurred across Britain, it is likely that the role played by large grazing mammals in our woodland history and development has been understated.
The Changing Face of Woodland
Following the retreat of the ice sheet after the last ice age, the climate gradually warmed up and plants gradually returned, culminating in woodland. As the climate changed, so the species composition changed, with the pioneer species such as alder and birch giving way to the longer-lived, large seed-bearing trees such as the oaks, beech and horn-beam. The woodland that is composed of these longer-lived species is sometimes called the climax vegetation.
Initially, the human impact on the natural woodland would have been minimal. As hunter-gatherers, the Mesolithic population would have been scattered, with the forest home to small numbers of families. Only later, once settled communities grew, did forest clearance take place, and so began the transformation of the landscape into one we would recognize today.
The pattern of clearance varied considerably in different parts and regions of Britain. While the Lowlands of Scotland were cleared quite early on for grazing, and were substantially cleared by the Middle Ages, the Highlands retained their woodland well into the 18th century. By contrast, the South Downs in Sussex were cleared of large swathes of woodland by Neolithic times, and then saw a return to woodland during the so-called Dark Ages. Even with flint axes, Neolithic man was able to clear large areas of wooded land quite quickly. Helped along by fire, grazing and the ring-barking of standing trees, substantial inroads were made into the natural woodland cover.
Clearance of Woodland for Farming
In Britain, the clearance of woodland started on the lighter chalky soils and the sandy heaths where it was relatively easy to clear the tree stumps and to till the land. In response to the development of settled com munities, the clearance for agriculture gathered pace and the population of Britain increased. Since the earliest human settlements, wood has played a key role in the development of wealth and power. As a primary natural resource, easily worked and with a multitude of uses, wood has played a part in the development of every civilization from the ancient Mesopotamians in the Fertile Crescent to the people of today and the ongoing exploitation of the tropical rainforests.
Most of the uplands of Britain are now bare of trees, with the result that erosion is a major factor in management and restoration.
Woodland cover in Britain from the last ice age to the present day. The reversal of large-scale woodland clearance in modern times is almost unprecedented.
Britain has a maritime or oceanic climate, with nowhere more than 110km from the sea, and is ideally suited to a pastoral farming system. The clearance of woodland for grassland and grazing was the foundation upon which agriculture developed.
The clearance and, much later, management of the major woodland tree species served to build our transport infrastructure, to house the growing population, to defend our shores and to build a trading nation and, later, the Empire. The ‘noble hardwoods’, among them the oak, ash and hornbeam, contributed immensely to wealth creation and employment, and were the ‘hearts of oak’ on which naval power was built.
Britain was substantially cleared of much of its primary forest or wildwood by the time the Romans arrived. The historical low point at the start of the 20th century led directly to the formation of the Forestry Commission in 1919 and the subsequent rise in the area of land planted with introduced conifers. What is not generally recognized, however, is that there has been a considerable increase in the area covered by broadleaved woodland, which in England currently stands at its highest for many centuries.
Uses of Wood
The varied structure found within woodland and the different growth rates of trees allowed a variety of types of building material to be grown on the same site. For example, trees that need a lot of light grow to form the upper storey of a woodland canopy, and these may provide the large timber; the more shade-bearing species such as hazel grow beneath the canopy as smaller-diameter material, forming what used to be referred to as the underwood. This material was more easily worked and harvested.
The methods of management used also reflected the technology available. With simple hand tools, it was small-sized produce, easily cut and shaped, that was preferred. The advent of metal tools, and later of power tools, enabled larger material to be transported long distances and to be manufactured off-site.
Species Preferences
Our woodland trees are extremely versatile. From the earliest times, it became apparent that certain species grew better than others, that some were more demanding of soils and exposure, and that some regenerated with less effort than others. Similarly, certain timbers were better suited to specific situations, and the trees could be manipulated while they were growing to meet specific local needs.
For these and other reasons, certain trees were preferred to other species, and were either planted or regenerated in greater numbers. This meant that the composition of the natural woodland altered in favour of certain species that had greater utility. For example, beech was favoured for chair making (bodging), particularly in the Chilterns, while in parts of the Weald of Kent and the Lake District, oak was managed for charcoal.
After many centuries of use and management, the woodlands reflected both the local climatic conditions and the uses the inhabitants made of them. Since we were, initially at least, woodland dwellers, then sites also tend to retain artefacts, dwellings and archaeological remnants of settlements. In many cases, woodlands remain one of the few places in which a strong link with the past is retained. Even when the trees are removed, the underlying soil tells a story in the accumulation of pollen built up in layers over a long period. It is for this reason that many of our ancient trees and woodlands are at least as important as ancient buildings in defining who we are and where we have come from.
Broadleaved woodland and farmland on the Sussex Downs. Note the clear boundaries between the farmland (on easily cultivated chalk) and the woodland.
Ancient or Veteran Trees
Recently, there has been renewed interest in what are termed ancient or veteran trees. Often found isolated in fields or hedgerows, they represent a link with a more wooded landscape and, in their shape and location, tend to reflect past management practices.
Types of Management
Historically, woodland was managed in a number of different ways, depending upon the type of material to be harvested, the species of tree being managed, and the availability of tools and the necessary skills. As technology developed so the ability to fell and to utilize larger-diameter timber grew. This necessitated new approaches to management and the evolution of a range of different silvicultural techniques and systems (see Chapter 10).
A more scientific approach to woodland management became evident in England with the publication in 1664 of John Evelyn’s classic account of woodland management and plantation silviculture, Sylva. Woodland owners also became more interested in managing their trees and in experimenting with new species and methods of establishment. The increase in area of privately owned plantations during the 17th century was a direct result of many of the landed gentry indulging in their new-found hobby of ‘forestry’.
Coppice
The earliest form of management, coppicing relies on the ability of many, mostly broadleaved, species to regenerate from a cut stump or ‘stool’. This technique produces small-diameter material ideally suited to hand working. Most of our native broadleaves coppice, and the time between successive cutting periods – the coppice cycle – may vary considerably between species.
An ancient yew, certainly well over 1,000 years old, in the Borrowdale Valley, Lake District, England. Shortly after this picture was taken a larger part of the tree was destroyed in the gales that swept Cumbria in January 2005.
Woodsman cutting oak bark for tanning leather in coppice woodland in Sussex in about 1890. Note the other produce in the background and the landscape, which is recognizable today. Oak bark is still cut for tanning, although on a much reduced scale.
Coppice with Standards
This allowed the production of both small-diameter material and larger sawlogs by growing a proportion of mature trees among the coppice. In some cases, the same species were used for both while, in others, notably hazel coppice with oak standards, the different species were used for specific markets.
Overstood Coppice
Now very common with the demise of the coppice industry, overstood or neglected coppice has been left past its traditional cutting cycle. Many of these woodlands are now in desperate need of management, which might entail a resumption of coppicing or conversion to another system.
High Forest
This is another traditional approach where trees are allowed to grow straight and tall and form a closed canopy. Usually having a number of levels or strata, the dominant trees may be a single species, or a number of different species, sometimes chosen to make the best use of the differing light levels found within the woodland. High forest can be managed in many different ways and with varying degrees of complexity.
Neglected coppice is sometimes converted to high forest, by ‘singling’ the multiple stems that arise from a cut stool. In cases where the neglect has been pronounced, the coppice may have already grown tall enough to form a closed canopy, but might be quite unstable and prone to wind damage.
A profile through a broadleaved high forest of oak, ash and hazel, showing the structure typical of temperate woodland in Britain.
An ash pollard recently cut to promote new growth and maintain vigour. St Johns-in-the-Vale, Cumbria.
Pollards
This is a specialized type of coppice designed to keep the young shoots away from grazing animals, particularly cattle. Often seen as isolated trees in fields or in hedgerows, most pollards tend to be long-lived and often ancient. In addition to pollarding, other specialized forms of management, still quite common in some European countries, included pleaching, shredding and suckering.
Wood Pasture
This is a form of ‘agro-forestry’, where stock graze between widely spaced large trees grown for both shelter and timber. Many wood pastures are now neglected and suffering from a lack of active management. Some historians believe that wood pasture was far more common than is often supposed.
Plantations
Plantations are usually established with the primary purpose of growing timber. They may be planted on bare land, or converted from existing woodland by felling and replanting with other species. They make up a large proportion of the woodland cover in Britain.
Past Management Practices and Ancient Woodlands
When managing woodland it is important to appreciate how past management affects the options for the future. Just as a ‘listed’ building needs protecting and conserving, so, too, do certain types of woodland. Table 2 summarizes the key features of the designated types and the commonly accepted terms used in designating woodland. We will see later how these designations may affect the options for future management.
To the best of our knowledge, all the natural woodland in Britain has been altered in some way. Even in the more remote regions, the vegetation will have been changed either by man’s activities or by the actions of domesticated or feral stock. Even in mainland Europe only small remnants of truly natural woodland remain in the more isolated regions of countries such as Poland, Finland and Romania.
Designations
During the late 1980s, it became apparent that many ancient woodlands were still being cleared for farming and development. In response to these threats, an Ancient Woodland Inventory (AWI) was completed for England and Wales on a county-by-county basis. This was followed in the late 1990s by one for Scotland.
Many of these designations might at first appear confusing or even arbitrary. In fact, in some cases the distinctions are either difficult or even impossible to make on the ground. Woodlands are in a continual, albeit long-term, state of change.
Many of our oldest woodlands, despite being irreplaceable, still lack any formal statutory protection. At the time of writing, fewer than 15 per cent of ASNW sites are formally protected, and PAWS woodlands have even less formal protection.
Each of the designations is explained in a little more detail below.
Ancient Semi-natural (ASNW)
This term reflects the fact that even the oldest of our woodlands have been altered at some stage in the past. However, these woodlands retain a strong historical link with the natural landscape, and are defined as having been wooded continuously since at least 1600 (prior to 1750 in Scotland) and being composed of species native to the particular site. These dates correspond approximately to the period when large-scale new woodland planting became more common, particularly on private estates. In conservation terms, they are of immense importance, and are the direct descendants of our once extensive and complex post-glacial woodland.
The term ‘semi-natural’ implies the regeneration of locally native species by either seedling or vegetative reproduction, rather than by planting. In the case of coppice, this might include ‘layering’. The woodland would therefore regenerate itself in clearings or following wind damage. One of the positive outcomes of the 1987 hurricane that hit the south-east of England was the opportunity to monitor the regeneration of woodlands following a large-scale natural disturbance. Rather than clearing all the fallen trees and replanting, areas were left untouched. The succession of plants, the competition between them and the woodland structures resulting from this, are all now being monitored.
Scots pine growing near the natural tree line in the Highlands of Scotland at Rothiemurcus. The altitude here is 550m and grades into a sub-alpine tundra above the sparse woodland cover. (Photo: Ted Wilson)
The structure and species composition of every woodland differs considerably, and reflects the local soils and climate as well as past management practices. Many of these woodlands would have existed prior to the large-scale changes brought about by agriculture, and therefore retain a link with the preindustrial landscape. They are now often isolated and fragmented, and one of the real challenges in future is to connect them with new and more recent plantings, and thereby increase their size. The conservation value of these woodlands, from both an ecological and cultural perspective, increases with size. Small woodlands have a proportionately longer ‘edge’ than larger ones, and the micro-climate effects and susceptibility to wind and exposure are more pronounced.
Plantations on Ancient Woodland Sites (PAWS)
In contrast to agricultural practices that tend to entail complete disturbance of the soil, the replanting of an ancient semi-natural woodland with another tree species will not destroy many of the important historical features of the site. For example, the soil and the seed bank will remain substantially intact, and the archaeological features may remain undisturbed in many cases. With careful management and financial support these Plantations on Ancient Woodland Sites (PAWS) may be restored.
Ancient Plantations
This sub-category includes plantations established pre-1600 using native species (as, for example, on a large private estate for the production of oak timber, or conifer plantations using introduced species established on ancient sites). These sites will vary greatly in their importance for conservation, and in many cases it will be difficult to distinguish them from the ASNW above, particularly if planted with native species.
Recent Semi-natural Woodland
This category includes a wide range of woodland types, but all are characterized by the regeneration of locally native species, often on heathland or moorland. Many woodlands on disturbed industrial sites such as old quarries or disused railway lines, together with areas of birch scrub, will come into this category.
Younger woodlands will be composed predominantly of pioneer species, while the older post-1600 woodlands might include species such as ash, oak and beech. In some cases, these woodlands will include native species regenerating outside their natural range, such as beech in the north of England.
Farmland left under set-aside schemes may well revert to this type of woodland, particularly if it is adjacent to existing woodland and if grazing pressures have been reduced.
Recent Plantation
This is a large category and includes all the plantations established by the Forestry Commission since 1919 and private forestry companies since the 1960s. In addition, it includes extensive plantations established by private landowners during the 20th century. Many of these plantations are composed of species introduced by the great Victorian plant hunters of the 19th century, including Douglas fir and Sitka spruce.
This category also includes many of the great landscaped parklands of the 18th century, together with smaller woodlands planted in the lowlands for shelter and game.
Many recent plantations are of very high landscape or amenity value and, increasingly, they are seen as important for wildlife, too. In some cases, these plantations will not be felled when the timber is ready, but will be left to grow on to ecological maturity. In some regions of Britain, plantations are reserves for the native red squirrel, and play host to wildlife as diverse as the osprey and the wild cat.
Woodlands on the March
There is a commonly held view that the area of woodland in Britain is decreasing, and that there is an urgent need to ‘do something about it’. While there are real concerns about the decline of specific woodland types, notably ancient woodland, and of individual ancient trees, the reality, at least in the temperate regions, is a little different.
Whether we are talking about Britain, Europe or North America, both the area of woodland and the volume of timber is increasing year on year. In fact, the area of woodland in Europe is currently at its highest for many centuries, while in North America far less than the annual new growth (increment) is felled for timber each year. In Britain, woodland has increased from some 9.2 per cent of the land area in 1980 to 11.6 per cent at the time of the last census carried out by the Forestry Commission in 1998; in Scotland the figure is even higher, with some 17 per cent of the country now under woodland.
Simply put, woodlands are in general better managed, used more efficiently and carefully, and are growing faster, than at any time within recent history. The reasons for this include:
• The timber that is felled is used more efficiently in modern mills, and technological advances enable smaller-diameter material to be utilized.
• Advances in measurement and mapping, and the development of computer-based information, has ensured that the resource is better used.
• The development of systems for certifying the good management of forests has resulted in more woodlands being carefully managed rather than exploited.
• Advances in tree breeding and methods of selection ensure that the species chosen for new planting schemes are better suited to the site.
• The warming of the climate over the last few hundred years and, in particular, the increasing levels of CO2 in the atmosphere, mean that trees are actually growing faster than they have in the past.
• Changes to agricultural practices, particularly in the uplands, have resulted in new woodland creation, sometimes as a result of natural regeneration.
• The enlargement of the European Union has brought in countries with extensive areas of woodland, many of which have been under careful management for centuries, but under-utilized in their previously stagnant economies.
• Increasing concern for, and interest in, the environment has resulted in an increase in the number of woodland owners.
• Charities for the conservation of woodlands, specifically the Woodland Trust in Britain, have prospered. They have been successful in promoting both new woodland planting and buying and managing existing, primarily broadleaved, sites.
• There is increasing interest in wood as a sustainable and renewable natural resource with very little ‘embedded energy’ used in its production. Architects are increasingly specifying wood for use in new buildings, and research is currently under way in identifying appropriate construction techniques for timber-framed buildings suitable for the damp British climate.
The plight of many of the natural forests in the tropics is a serious cause for concern, but somewhat outside the scope of this book. However, by better managing, utilizing and expanding our own woodlands, the pressures on some of the natural tropical forest resource may be partially reduced.
CHAPTER 2
Getting to Know Trees and Woodlands
Woodlands and forests cover nearly four billion hectares of the Earth’s surface, over 30 per cent of the total land area. Within them live some of the largest, heaviest, oldest and tallest living things on the planet: trees. The trees in turn support myriad other plants and animals to create distinct woodland ecosystems.
Over many millions of years trees have evolved the ability to grow in many different climates, ranging from the Arctic Circle to the Equatorial swamps. Some are survivors from before the dinosaurs roamed the Earth, little changed in structure or shape (the conifers), while others have evolved into more complex forms (the broadleaves).
This chapter is designed as an introduction to how trees grow, how wood is formed, how they live together in woodlands and how we can recognize the types of woodland we see all around us. Finally, we will look at some of the ways in which we control the growth and development of woodlands, through the use of silviculture.
As time and space is limited, we will consider only those trees and woodlands from the northern temperate zone, and more specifically from Europe and Britain. Many tropical and subtropical trees and forests adopt quite different strategies for survival and reproduction, and their ecology is complex in ways sometimes quite different from our own trees and woodlands. By understanding these things better, we will be able to appreciate how and why woodlands are managed today.
Some of the oldest and most biologically diverse forests are found in the tropics. This forest giant in Tobago emerges from the canopy within the ‘Main Ridge Reserve’ established in 1765, one of the oldest protected reserves in the world.
What is a Tree?
The definition varies, but often a tree is defined as a woody perennial with the capacity to grow a single stem of at least 6m in height. Not very inspiring! However, this definition clearly distinguishes a tree from a shrub or other flowering plant, although some trees may also be shrublike if conditions allow.
It is this ability to grow a straight stem, capable in some species of reaching over 100m in height, that leads to the complex ecosystems we call forests and woodlands. Growing from this stem are many different structural elements designed to capture sunlight, provide shade, absorb oxygen and expel other gases.
The main parts of a tree are:
Above Ground
• Leaves These convert energy from sunlight into carbohydrates (sugars and starch).
• Reproductive structures Male and female reproductive structures can be present on the same tree, or on separate trees, depending on the species.
• Branches These support leaves and reproductive structures.
• Stem This provides support for the tree crown, and transports water and minerals from the roots to the leaves, and sugars from the leaves to the roots.
Below Ground
• Structural roots These give stability, transport water and mineral nutrients, and are also used for the storage of starch.
• Fine roots These facillitate the uptake of water and mineral nutrients.
• Mycorrhizae A fungus–tree partnership that enhances the uptake of water and certain mineral nutrients.
Simplified diagram showing the movement of carbohydrates, water and mineral nutrients. Carbohydrates formed in the leaves descend to the roots (A); water and mineral nutrients move up from the roots (B).The leaves take carbon dioxide from the air and ‘fix’ the carbon, releasing oxygen in the process.
How Does It Grow?
This is quite a complex subject. A number of different things occur in a number of specialized cells and structures.
