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(WITH P.A. WOLSELEY) RIVER VEGETATION: ITS IDENTIFICATION, ASSESSMENT AND MANAGEMENT. 1981. A Field Guide to the macrophytic vegetation of British watercourses. Cambridge University Press, 154 pp. ISBN 0—521-23186-8.

PREFACE

This book identifies and classifies the plant communities found in British streams, dykes and canals, assesses damage and pollution, and gives the probable effects of other activities of man, from trampling to the construction of reservoirs. It therefore forms a manual for watercourse vegetation and its management. It is written for non-specialists - for anyone able to name plants, or able to use a simple book to do so. References are given to other sources of information.

Chapter 1 describes a simple method for surveying watercourse vegetation, and discusses identification. The procedure used for stream community classification is given in Chapter 2. Chapter 3 describes the principal stream communities found throughout Great Britain. Naturally, some local variants are not included, but these usually resemble, or can be deduced from the communities listed. Chapter 4 investigates the extent of damage in streams. This can be quantified in most lowland streams, and some hill ones, by comparing the actual vegetation found with that described in Chapter 3 as the 'correct' vegetation for the particular habitat. Damage can be physical (e.g. cutting, altering flow), or chemical (pollution). If there is little or no physical damage a pollution index can be used. Chapter 5 describes the vegetation of dykes and canals, and provides a rating scheme for these. The final chapter summarises the effects of different types of man's activities, providing a guide to the results of management and disturbance. It can be used both to predict, and to explain, changes in vegetation.

The vegetation described in Chapter 3 and parts of Chapter 5 is, for the purposes of this book, termed 'undamaged'. In Britain, only a few mountain streams have been unaffected by man: all lowland streams are managed, often intensively, and dykes and canals are man-made and depend on management for their existence. Further, much of Britain was originally covered by forest, which therefore shaded streams and confined their vegetation to intermittent openings in the tree canopy (and the central parts of larger rivers that could not be shaded). 'Undamaged' vegetation is, therefore, quite a different concept to 'natural' vegetation: natural vegetation is that which is unaffected by man, while undamaged vegetation is that with diversity, cover and quality as high as can be found in unpolluted British streams at the present time. The long-term effect of traditional management patterns is to maintain undamaged vegetation, though the short-term effects of these (e.g. dredging) and twentieth-century techniques (e.g. major re-channelling, herbicides) may be to cause damage.

Chemical assessments of pollution have been used in Britain since the early years of this century, with increasing sophistication. Invertebrate pollution indices, particularly the Trent Biotic Index, have been in use for several decades, and indices using other animal or plant groups (e.g. fish, algae) have occasionally been used (see J.M. Hellawell (1978), Biological Surveillance of Rivers. Water Research Centre). This book introduces plant (macrophyte) monitoring for Britain. There are several advantages in thus using the larger plants. First, botanists are more concerned with the effect of pollution on plants than on, say, fish. Also, if water is wanted for crop irrigation, then assessment by plants is the obvious choice. (However, even if potential irrigation water is clean on the plant index, pilot tests should be run on the crop(s) to be irrigated, as some crop species are exceptionally sensitive to pollution.) Another advantage is speed: macrophyte monitoring can be done in minutes, while invertebrate monitoring takes hours, and chemical assessments days. This is because the plants are easy to record, being both large and stationary (though they can be surveyed only in summer, as many die back in winter). When a river is recovering from pollution, plants can be valuable indicators of when water can be abstracted, because the plants are rooted in, and so affected by, the soil (the substrate) - and it takes longer to wash out polluted substrates than it does to substitute clean water. It is important that the substrate is clean if storm flow water is to be abstracted, because during storms silt from the bed is carried in the water, so if the silt is toxic the storm flow water will also be toxic. So even if the chemical and invertebrate indices report, quite correctly, that the water is clean, storm water should not be abstracted until the plant index reports the silt is clean also. Finally, and, for watercourse quality assessments, most important, it must be remembered that all the different animals and plants and (measured) chemicals reflect somewhat different aspects of that watercourse quality. Therefore it is only when each and all methods find a river clean that it can be assumed to be truly clean. If either the invertebrate or the macrophyte indices find the habitat polluted, it is so.

This book is for use in England, Scotland and Wales only. There is a general resemblance of vegetation types in different countries of Europe, but there is seldom an exact correspondence between, for example, sandstone streams in Belgium, Germany and Britain. The descriptions of communities given here therefore vary from being almost the same as those for watercourses outside Great Britain to being merely similar (and, as can be seen from Chapter 4, etc., a slight difference in the 'expected' (undamaged) vegetation renders the damage rating useless). The principles described here are international; the details, unless modified, are not.

CONTENTS

Preface

1 Surveying a watercourse

Introduction; equipment, etc., needed; time of survey; sites for survey; number of sites to record; recording in the field; records to be completed in the lab or at home.

2 Identifying stream communities

Introduction; stream size: inner white dial; landscape type: middle white dial; rock type: outer white dial; colour band dial; directions for using the stream dial.

3 Descriptions of stream communities

Introduction; chalk streams; oolite streams; clay streams; soft sandstone streams; New Forest sands streams; alluvial streams; streams on mixed catchments (soft rocks); resistant rock streams; hard sandstone streams; hard limestone streams; calcareous and fell sandstone streams; coal measures streams; streams on mixed catchments (hard rocks).

4 Stream damage rating and pollution index

Introduction; assessment of damage rating; assessment of pollution index.

5 Dykes, drains and canals

Introduction; dykes and drains; canals.

6 Effects of man's activities, etc.

Interference associated with channel maintenance; interferences associated with use of water and watercourses; interference associated with agricultural practices.

Rock type map

Glossary

Index to sections

Abbreviations of plant names on stream dial

Stream dial

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