84

AGE AND GROWTH RATE OF TROPICAL TREES

Age and Growth Rate of Tropical Trees. Proceedings of the Workshop on Age and Growth Rate Determination for Tropical Trees, held at Harvard Forest, Petersham, MA, April 1--3, 1980. F. Herbert Bormann and Graeme Berlyn (Editors). Bulletin No. 94, Yale School of Forestry & Environmen- tal Studies, 1981, 137 pp., US$6.95.

The work brings together in a little over 100 pages most of what is known on the subject. More than this, by evaluating patterns and processes of growth ring formation and aging, which makes it possible to determine age and growth rates relatively readily in temperate trees, the book points the way to re- search on the determination of these attributes in tropical trees.

The book comprises Bulletin No. 94 of the Yale University School of Forestry and Environmental Studies and also the proceedings of a workshop, held at the Harvest Forest, Petersham, MA, U.S.A. in 1980. The workshop brought together 27 scientists -- regrettably none from the major tropical forest regions of Africa or South-East Asia -- with the objective of identifying 'promising lines of research for the measurement of age and growth in tropical trees'.

A brief preface discusses the justification, sponsorship and organization of the workshop. Three introductory chapters define and elaborate the prob- lem.

Chapter 1, written in anecdotal style (Ashton), illustrates the need for in- formation on age and growth rates in clarifying problems of tropical forest dynamics, particularly questions of ontogenetic specialization and succession which have implications for silviculture. Chapter 2 (Tomlinson and Longman) discusses observations on phenology of tropical trees against the background of the known behaviour of temparate trees. The main conclusions reached are that in tropical trees, architectural diversity introduces complications when studying the correlation between crown behaviour and cambial activity and that there is uncertainty about the extent to which cambial activity, and hence growth ring formation, are related to crown development and season- ality. The final introductory chapter (Mariaux) reviews past efforts and tech- niques used in measuring age and annual growth in tropical trees.

The remaining seven chapters embody reports by the working groups, into which the workshop had been divided for in-depth study of possible contri- butions to the subjects, from the disciplines of wood anatomy, wood chem- istry, radioisotopes, dendrochronology, demography and biometry.

The group on wood anatomy reviewed again past studies on tropical trees, inevitably repeating much of the content of earlier chapters. Classification of tropical trees, by this group, into those with and those wi thout distinct growth rings was useful in defining research needs. For those with distinct growth rings, the main questions to be setteld are the number of rings formed annually and the identification of false rings. For trees in the second group,

85

identification of the structural features that can be used to detect cyclical changes is still the main challenge. The group reviewed and tabulated prom- ising anatomical characters and recommended for closer s tudy the variation in length of Xylem elements, using techniques described as static (on non- living samples) or dynamic (involving living trees). The tables and appendices on techniques and current status of knowledge on growth rings of tropical trees, and the fact that the approaches discussed involve relatively inexpen- sive and non-elaborate instrumentation, undoubtedly make this chapter the most useful in the book for workers in the tropics.

Reports by the remaining groups provide useful insights into techniques of wood chemistry, radioisotopes, dendrochronology , demography, inventory and mathematical modelling that can be applied to the study of age and growth rates of tropical trees. Many of the suggested techniques require elaborate and expensive instrumentation and advanced skills, all of which are not readily available in the countries where tropical trees grow. Perhaps these chapters underline the need for collaboration between workers in the tropics and those in countries with advanced laboratory facilities and skills. It is particularly for reasons such as this, that the non-inclusion of workers from tropical countries in the workshop that gave rise to this book is regret- table.

The set of general recommendations which concludes the bulletin suggests practical steps that should be taken by the International Scientific Commu- nity and funding agencies to promote co-operative s tudy of the problem. Major activities to be undertaken by collaborative effort are underlined and include the establishment of a data bank, permanent s tudy sites and a news- letter for disseminating information about progress on the subject.

Altogether, this book is invaluable for anyone working on tropical trees in forests.

Although it does no t provide ready answers to the vexed question of aging of tropical trees, it contains adequate reviews and recommendat ions to serve as a practical guide to field workers and any that may wish to study the prob- lem further.

D.U.U. OKALI University o f lbadan

Department of Forest Resources Management Ibadan Nigeria