Distribution and ecology of vascular plants in a tropical rain forest: Forest vegetation in Ghana

394 Pages·1981·32.2 MB·English

by  J. B. Hall

Distribution and ecology of vascular plants
in a tropical rain forest
Geobotany 1
Series Editor
M. J. A. WERGER
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. 1981
J. B. HALL AND M. D. SWAINE
Formerly of Departmem of Botany, University of Ghana, Accra
Distribution and ecology of vascular plants
in a tropical rain forest
Forest vegetation in Ghana
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. 1981
This volume is listed in the Library of
Congress Cataloging in Publication Data
ISBN 978-94-009-8652-7 ISBN 978-94-009-8650-3 (eBook)
DOI 10.1007/978-94-009-8650-3
Cover design: Max Velthuijs
Copyright © 1981 Springer Science+Business Media Dordrecht
Originally published by Dr W. Junk Publishers, The Hague in 1981
Softcover reprint of the hardcover 1s t edition 1981
All rights reserved. No part of this publication may be reproduced. stored in a retrieval system. or transmitted in any form or by any
means. mechanical. photocopying. recording. or otherwise. without the prior written permission of the publishers.
Springer-Science+Business Media, B. V.
Dedicated to Albert Adai Enti, who was our first
guide in the Ghanaian forest, and whose under
standing and knowledge of its plants have been a
constant source of information and inspiration.
Foreword
It is a privilege to be asked and a pleasurable duty for me to write the foreword of this book.
The conservation and wise utilisation of the humid tropical forests, a unique biome, are matters of great
concern and importance to millions living within and around these forests and, perhaps, less directly, to the
totality of mankind.
These forests provide many essential products and services for mankind. The list is lengthy and need not be
repeated here. Suffice it to say that there are not many aspects of human activity which do not utilise some of
these products, services or derivatives therefrom. Yet it is the view of those most closely associated with the
study of these forests that what is known is but a minuscule portion of whatthere is to know. The products
and services now utilised, are perhaps some infinitesimal part of the full potential.
All over the tropical world, however, these forests are being destroyed. At first, slowly, but now surely
gathering tempo. This is true also of Ghana. Tracts offorest land are converted to other uses, often ephemeral
and not sustained. Irreversible changes take place in our environment. The gains are shortlived, the losses
unobtrusively accumulate and stay forever. The accelerating rate of deforestation, in the face of our relatively
scanty knowledge of this biome, is indeed a sad reflection of the state of human affairs.
It is in this setting that one welcomes this book by Messrs. J. B. Hall and M. D. Swaine.
John Hall came to Ghana in 1955 as a Biology master at Mfantsipim School, Cape Coast, moved in 1964 to
the University of Cape Coast (then a University College) as a Botany Lecturer, and worked from 1966 to 1980
as Lecturer and Senior Lecturer at the Department of Botany, University of Ghana, Legon. He has collected
plants in all parts of Ghana, was in charge of the Ghana Herbarium from 1969 to 1980 and has published
widely.
Mike Swaine joined the Department of Botany, University of Ghana, Legon in 1971 and worked as
Lecturer and Senior Lecturer till 1979. His degrees in Forestry and Botany at the University College ofN orth
Wales prepared him for the association with John Hall. Together they roamed the remotest parts of Ghana,
collected, described and wrote. Mike Swaine, as I write, is now with the Institute of South-East Asian Biology in
the Department of Botany, University of Aberdeen, Scotland.
This book is the result of a survey of the floristic composition of the closed forest in Ghana. It introduces
the ecology and utilisation of Ghanaian forest in relation to work on tropical forest elsewhere. Full
descriptions offorest types are given and concentration is on the more detailed species distribution, including
herbs and shrubs, from which the forest classification is derived.
Excellent maps show the distribution of species most commonly found in the plots assessed, the localities of
herbarium specimens, the plots the authors found the species in, and notes on the life form, reproductive
morphology and ecology of each species together with references of taxonomic treatments.
I consider this a very important contribution to knowledge of the humid tropical forest in Ghana.
In a sense this book should update and complement earlier workers; Hutchinson and Dalziel 'Flora of West
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Tropical Africa', Taylor 'Synecology and Silviculture in Ghana' and Irvine 'Woody Plants of Ghana'. I pay
tribute to those earlier workers and also to these latest.
This book should be of great interest to a wide variety of people: botanists, ecologists, foresters,
geographers, pharmacists, taxonomists, teachers, students and all users of forests.
I hope it improves their perception of overall forest composition, of species regeneration, of areas where
conservation is most necessary, and spurs them on, one way or the other, to save this invaluable asset.
J. H. Fran90is
Chief Conservator of Forests
Department ofF orestry, Accra
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Preface
Of the world's major ecosystems, tropical forest is the most complex both architecturally and floristically
and, largely because of this complexity, the least understood. In comparison with most tropical forests, those
of Ghana are well known, at least taxonomically. Herbarium collections span 200 years. Botanists and
foresters have visited every part of the forest zone. Its plant species are described in a comprehensive Flora of
West Tropical Africa which has gone through two editions. Although new species continue to be found and
described, they are encountered very seldom. The taxonomic foundation has therefore been laid for an
account not merely of the occurrence of forest species in Ghana, but also of their distribution within the
country.
Information on species distribution can be gleaned from the localities of herbarium specimens cited in
Floras, or from the labels of specimens in large herbaria, such as the Ghana Herbarium in the University of
Ghana, Legon. Such information will be reliable as far as it goes, but very incomplete. Botanical collectors,
naturally enough, have concentrated their attention on accessible places near main roads and towns, and on
those low-growing species with accessible flowers, and especially on species which flower for much of the
r
year. Foresters get off the beaten track, but their main interest is in large trees. The smaller trees, and
especially the large climbers, have been generally neglected.
Between 1971 and 1975, we undertook a survey of the floristic composition of Ghanaian closed-canopy
forest. We listed all vascular plant species present on 155 sample plots in mature forest, each plot measuring
25 m X 25 m, distributed throughout the forest zone; the number of plant species on each plot ranged from
20 to 200. Species were also listed on a further 130 plotless samples. Of a total 1 300 species recorded (out of a
total forest flora of 2 000 species), the 749 which occurred four or more times were used for ordination. Our
new classification of Ghanaian forest (Hall & Swaine 1976) was derived from this ordination. A byproduct of
the survey was much data on species distribution, and the presentation of this data is a major aim of this book.
Of the 749 species ordinated, we have not mapped those whose distribution was very sparse and
uninformative, and were therefore not adequately represented in our survey records. Our 624 maps therefore
show the distributions of that third of Ghana's forest species which are most commonly encountered in
mature, non-swampy forest. It is unfortunate in some ways that secondary forest species have had to be
omitted, as this group includes many important medicinal plants such as Rauvolfia vomitoria, and Voacanga
africana, and the most promising of the sources of sweeteners, Thaumatococcus daniellii.
Each map shows our survey records by solid dots; because sample plots were scattered fairly uniformly
through the forest zone, and all species present were recorded, it is possible from the distribution of these dots
to draw conclusions as to relative abundance and dispersion ofthe species. Some species are seen to be evenly
spread throughout the forest types in which they occur, whilst the distribution of others seems to be
influenced by historical rather than by ecological factors. From the reference maps, the plot numbers in which
any species occurs can be identified, and the exact location of each plot is given in an appendix. Using this
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information it should therefore be possible to find the species on the ground. The histograms accompanying
the maps are derived from sample plot data, and indicate the apparent ecological preference of each species.
Herbarium records are generally shown by circles. Where the locality for a herbarium specimen coincides
with that of a survey record, the former is generally omitted, though it is included, slightly displaced, in the
case of some rare species.
The brief notes accompanying the maps are intended to bring the taxonomy of the species up to date, to
indicate species in need of further taxonomic work, and to summarise life forms and phenology concisely and
consistently.
Distribution maps of African plants are listed by Lebrun & Stork (1977), and maps continue to appear in
the Distributiones Plantarum Africanarum series published by the Jardin Botanique National de Belgique.
The overwhelming majority of these maps show distribution on a continental, or regional scale, and it has
been suggested to us that the time is not yet ripe for attempting to map distributions within a single country.
Although we are only too well aware of the possibilities for error in field determinations, we can only plead
that we have done all we can to minimise these, by collecting specimens for verification in the herbarium, by
crosschecking between plots, and so on. Our maps are certainly imperfect, but it is equally certain that before
they can be substantially improved, much of the remaining forest will have given way to farms and timber
plantations.
Janzen (1975) begins his text on Tropical Plant Ecology with the words: 'It is my opinion that the study of
plant biology in general, and the biology of tropical plants in particular, has suffered greatly from over
emphasis on descriptive morphology, phytosociology, and systematics.' As our book deals with precisely
these three aspects of botany, perhaps we should apologise for inflicting yet more suffering. We hope
nevertheless that even the most adventurous ecologists may find here at least some raw material for their
daring generalisations.
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