Tropical Trees: Propagation and Planting Manuals

Volume 4

PREPARING TO PLANT TROPICAL TREES Contents

Written by K A Longman

Illustrated by R H F Wilson

February 1995

Commonwealth Science Council

Tropical trees are a valuable natural resource that has many different functions. Most species can help to restrain the rapid erosion of soil by water and wind. Trees can also maintain soil fertility, and some are particularly effective in restoring degraded farmland. In addition, trees provide a great range of important products, such as fuel, forage, food, medicines, housebuilding materials and agricultural implements as well as sawn timber, plywood and paper. Their presence is thus essential for many rural communities, besides contributing substantially to both urban and export markets.

Tree cover influences local environments, regional climates and even the global atmosphere. Tropical trees are important for their cultural significance, the biodiversity they represent, and the multitude of life they support.

Despite these many vital functions, tropical trees continue to disappear about ten times faster than they are replaced, thereby threatening the life-support systems of many human communities. Yet the forests and savannas, farmland and woodlands where they thrive could be managed sustainably, providing soil protection, supplies of products and other benefits in perpetuity.

The many inter-related reasons for this paradoxical situation include:

• the undervaluing of trees as a renewable natural resource
• the expectation that trees will just come up by themselves
• the assumption that farmland should be completely cleared
• ignoring of ecological rationales for successful land use
• the equating of economics with maximising short-term gains
• a lack of communication between the various people concerned
• bureaucratic delays and shortage of finance
• increasing human populations
• too much cutting, grazing and burning
• use of a single species over large areas
• an absence of research or experience in ‘domesticating’ most tree species
• problems with seeds, planting stock or establishment.

Tropical Trees: Propagation and Planting Manuals provide practical, illustrated guidelines to encourage widespread planting and care of trees. The series covers all stages from genetic selection through setting up a forest nursery to planting and successful establishment in the field (see inside back cover). Also included are sources of further information and supply of materials, and examples of check-lists, sketch maps and record sheets.

The Manuals are spiral bound so that pages can easily be photocopied for use in the field. We hope that the series will stimulate the writing of sheets specifically for local use.

© Commonwealth Secretariat 1995

Published by the Commonwealth Secretariat

May be purchased from
Commonwealth Secretariat Publications
Marlborough House, Pall Mall
London SW1Y 5HX, U.K.

ISBN 0 85092 418 9

Price £30.00

This manual may be reproduced in part for the purposes of education or to facilitate fieldwork

Prepared on behalf of the Commonwealth Science Council
CSC(95)AGR-22, Technical Paper 309

Typesetting by Advent Print Services Ltd., Hitchin, Herts.
Printed by the Commonwealth Secretariat.

PREFACE

It is ironic that the multiple value of tropical trees is just becoming appreciated as they are near to disappearing from some regions. Their many important roles are thus being recognised the hard way, as their removal leads to greatly accelerated soil erosion and loss of fertility, and to shortages of hundreds of useful products. This undermining of vital support systems for rural life is the most immediate and crucial threat to humans, but there are also serious consequences for nearby towns and cities, for other tropical regions, and indeed for people living elsewhere in the world.

“Where I live … you are lucky to see more than three trees standing together” sums up the feelings of many people in the tropics. Almost tree-less tropical landscapes can also be observed by people living elsewhere - in pictures and in TV programmes depicting areas formerly under forest, savanna or other woodland. All of us need to address the fundamental paradox: why kill the goose that lays the golden eggs? The many aspects lying behind this urgent question are tackled in this Manual.

Granted that tropical trees are very important and need to be much more widely planted, it may still be asked why one needs a set of manuals for something that seems straightforward. In practice, however, there are many potential pitfalls when choosing appropriate kinds of trees, and when growing good planting stock. The same is true for planting and establishing trees successfully - one can solve nine problems only to fail at the tenth. Preparing to Plant Tropical Trees deals with the key stages between propagation and planting, when the most frequent, varied and difficult problems arise.

This Manual covers both the humid and semi-arid tropics, providing a framework for considering diverse planting sites, choosing tree species for different purposes, deciding which types of growing system to use, and how to prepare the land. All sheets take as their background the general ecological principles that underlie tree survival, without losing sight of practical constraints on tree planting. Emphasis is placed on the choice of appropriate planting patterns, such as small groups, lines or strips, which can minimise soil damage and provide favourable environments for young trees to become established. The remarkable ability of some soil-improving trees and shrubs to protect bare land, and to reclaim degraded soils, is also covered.

In addition to prudent use of pure stands, the value of using mixtures of different kinds and sizes of trees in agriculture and forestry is stressed. Over-use of large, even-aged stands of a single introduced species during the middle decades of this century occurred when serious misapprehensions about tropical ecosystems were commonly held. Although it was neither promoted by tropical forest scientists, nor indicated from past experience, this extreme concentration on exotic monocultures nevertheless gained widespread acceptance amongst foresters and consultants.

A second dubious assumption during this period was that good agricultural practice and the rules of economics demanded that farmland should be cleared of trees. However, declining yields and the scale of soil loss from poorly protected land have led inexorably back towards agroforestry, and to efforts to blend local experience with scientific understanding, in order to promote tree planting and retention. A truer economic picture emerges when one includes the multiple roles of trees in protecting the soil, providing conditions for farming and for producing many of life's necessities, as well as creating the possibility of reclaiming degraded sites - now one hectare in every five.

Tackling such serious misconceptions is best achieved through good communication, which is needed in any case for successful tree planting. Another, more recent dogma suggests that no further research is needed, only the application of what is already known. On the contrary, all over the tropics there are numerous relevant local tree species that have neither been widely planted nor studied experimentally. Research, both formal and informal, is urgently needed, for instance on these undomesticated trees, on the many ways they might fit into existing systems, and on conserving natural stands which still contain them.

This Manual aims to present information and guidelines that can be applied to tropical trees in general, and to set out the various choices available as clearly as possible. Because of its subject matter, it contains rather less description of individual techniques than the other Manuals, but more consideration of the many relevant points. To assist the users - farmers and foresters, local inhabitants and overseas workers, large-scale growers and community groups - there are many cross-references, a comprehensive index and over a hundred line drawings.

During the short time it takes to read this preface, more than a thousand tropical trees have disappeared, and have not been replaced. Yet there is also encouraging evidence of a growing recognition of the links between trees and people's livelihoods, the increasing involvement of women, and the local planting, for example, of many kilometres of trees in shelterbelts, behind which “whole fields of crops are being grown”. The scale of the problems is indeed very large, but tree planting is becoming the concern of more and more individuals, groups and organisations.

Acknowledgements are made for use of photographs as a basis for some of the drawings in this Manual, including several from Longman and Jeník (1987), and from Hamilton and Snedaker (1984), Ramakrishnan (1992), the Permaculture International Journal and the Newsletters of Tree Aid (see D 70–71). I should also like to thank my colleagues in the tropics and in Edinburgh for a great deal of help and stimulation while writing these Manuals. They are intended to encourage local users to write specific sheets for particular species, and I shall also be happy to receive suggestions for additions and improvements for revisions and ideas for later Manuals.

Alan Longman
24 Orchardhead Road
Edinburgh EH16 6HN
U.K.

September 1994

The author, Dr Alan Longman, has worked in the West African tropics for 9 years, teaching plant physiology, doing research on trees and setting up a large nursery for vegetative propagation. He taught and supervised students at all levels, and his research into the growth and development of trees included studies of flowering and phase change, rooting of cuttings and early genetic selection, and the effects of day-length and temperature.

Starting as a forestry worker in 1949, Alan Longman has been a Senior Lecturer in the University of Ghana, Principal Tree Physiologist of the U.K. Forestry Commission and a Charles Bullard Fellow at Harvard University. He began a research project on tropical trees at the Institute of Terrestrial Ecology near Edinburgh, Scotland, which has now been running for more than 20 years.

He is on the Editorial Board of Biologia Plantarum, and has acted as a consultant to various organisations. In retirement, he is drawing together scattered items of scientific research, and combining them with local experience to make effective information and ideas available to others, particularly those interested in tropical trees.

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