Models in Ecology. by J. Maynard SmithReview by: M. B. UsherNew Phytologist, Vol. 73, No. 5 (Sep., 1974), pp. 1071-1072Published by: Wiley on behalf of the New Phytologist TrustStable URL: http://www.jstor.org/stable/2431541 .

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Reviews 1071

(Sx)2 for what is usually written (?x)2, and on p. 132 for what is elsewhere written as Sx2 or S(x2), normally written as Xx2. Such quirks do not assist the non-mathematical student who is implicitly catered for in the book as a whole. Transition from one edition to the other and incorporation of new material is not entirely smooth, resulting in wrongly cited cross-references and out-dated references to well-known books now themselves in revised editions. The Ap- pendices are not referred to at all in the text. Surprisingly, recent methodological work on pattern analysis is not reviewed. These and other minor deficiencies mar what can otherwise be recom- mended as a useful and clearly written account of one aspect of plant ecology.

P. S. LLOYD

Models in Ecology. By J. MAYNARD SMITH. 22 X 14 cm. Pp. xii + I46, with 48 text-figures and 3 tables. Cambridge University Press: London and New York. I974. Price ?3.70 ($10.50 in U.S.A.).

If reference is made to the ecological journals of the last decade or so, the trend towards the quantification of ecology is obvious. Quantification comes, however, from two sources. One source is statistical, and is concerned with the organization of experiments, the collection of data, and the testing of a priori hypotheses about the observed differences and relationships. A large number of books have been published on statistical methods for biologists. The second source is modelling, and is concerned with investigating the form of relationships, of interactions, of time-dependent processes, etc. This source of quantification in ecology has been poorly served with books, though some aspects of modelling can be found in such chapters as 'Popula- tion processes' in some of the more general ecological texts. Professor Maynard Smith's book is therefore welcome at this stage of development in ecological modelling.

After an introductory chapter, there are three chapters devoted to an understanding of predator-prey relations. These chapters give a broad view of modelling this interaction, but they demonstrate the authors preference for calculus models-matrix models are described as 'convenient both for practical calculation and for analytical studies', but they are then dismissed with a reference to two books in which they are described. For the student the calculus termin- ology might pose a problem with the unexplained change from dN!dt for the rate of change of numbers in the Introduction to dxldt in Section A of Chapter 2 to x in much of the remainder of the book. It is refreshing, however, to find that the basic ideas and assumptions behind the models are exposed. How many ecologists have appreciated that the logistic equation 'is the simplest differential equation with the two required features: (i) when x is small . . . growth is exponential, and (ii) as t increases, x approaches a steady value without oscillations'? This widely quoted equation is thus based on mathematical simplicity rather than on biological reality.

The fifth chapter describes models for competition and the sixth, dealing with the effects of migration on the predator-prey interaction, contains material that is largely new. This chapter is of interest to the general ecologist as it shows how often abstract studies on population dyna- mics can be related to the more observational aspects of ecology such as migration, energy flow or succession. Chapters 7-IO essentially deal with the subject of complexity and its relatiorn with stability. These four chapters are written extremely theoretically, and are indeed not illustrated by reference to any field or laboratory communities or populations. Perhaps this indicates that field and experimental ecologists still have a lot of research to undertake, and it might imply that the models will have to be modified when the behaviour of several real populations is known. The book is concluded with two chapters, one looking at genetical implications and the other dealing with territorial behaviour.

How effective is the book in reviewing the development of modelling in ecology? Three points can be made. First, the lack of illustration of formulae and models with the data of real popula- tions demonstrates the shortage of 'case law' in the ecological sciences. If the book stimulates researchers to collect data to test the models then it will have served the useful purpose of encouraging the development of the subject. Secondly, the depth of treatment of various aspects of modelling is variable. Many of the references are modern which results in the omission of some of the historical arguments. The value of the book as a general textbook on ecological modelling is reduced when one has to refer to other books, for example for matrix methods or definitions of competition. Thirdly, throughout much of the text, and not only in Chapter ii,

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1072 Reviews one is aware of the underlying genetical implications. It is fairly certain that the subjects of population genetics and ecology will add to the development of each other.

The book will be welcomed by mathematical ecologists. It is to be regretted that it is so expensive (the cost is a little over 2.5 p per page), thus reducing its possible use as a student text.

M. B. USHER

Vegetation of the Earth in Relation to Climate and the Eco-Physiological Conditions. By H. WALTER. Translated by Joy Wieser. 224 X 148 mm. Pp. xiv ? 237, with 79 text- figures (including photographs). English Universities Press: London. Springer- Verlag: New York, Heidelberg, Berlin. 1973. Price p245.

This is an abridged form of the author's two volume Die Vegetation der Erde (I964, I968) and was published in German as Vegetationszonen und Klima in 1970. The original work was widely praised as a remarkable synthesis and was critically and enthusiastically reviewed in Britain (Vol. i by Poore, Y. Ecol. 5I (I963), 496, and its 2nd edn in Y. Ecol. 54 (I966), 844; Vol. 2 by Grubb in Y. Ecol. 58 (1970) 315, and the English translation of Vol. i by Grubb in]. Ecol. 6o (1972), 940, and by Ashton in New Phytol. 71 (1972), 1245). These reviews indicate very ade- quately the strengths and the weaknesses of Walter's opus.

To this reviewer, Walter's remarkable achievement survives the strong compression from nearly I500 pages down to 244. He presents a coherent account of vegetation types and aspects of their eco-physiology. His bias to water relations comes over very strongly. There is very little on, for instance, mineral nutrition or soils.

Tropical rain forest occupies a bigger proportion of this book than of its predecessors but the account is extremely dated and highly misleading. To cite a single example, it simply is not true that 'the question of the regeneration of virgin forests in the tropics has scarcely been investigated' (p. 46). Quite apart from the work being undertaken at the Institut fur Weltforst- wirtschaft in West Germany this topic has in fact been one of the major preoccupations of foresters in the humid tropics for at least fifty years. If, on to the updated map (Fig. i) of Walter's peregrinations around the globe, is superimposed a map of the tropical rain forest regions, it is seen that he has still only skirted round this major Formation even though he has added to his travels since the first volume first appeared, and even though his critics have consistently remarked on his bias to arid and semi-arid vegetation Formations.

The book can be recommended as good reading for students, but not in isolation from other texts. In an age of fragmentation it is nice to see vegetation types well described, differences between the same Formation in different continents expounded, the whole set as a framework for discussions on water relations as an important causal factor. But the bias of the treatment must be realized and Chapter I on evergreen tropical rain forest regrettably is better ignored.

T. C. WHITMORE

A New Ecophysiological Approach to Forest Water Relationships in Arid Climates. By I. GINDEL. Pp. 142. Dr. W. Junk B.V.: The Hague. 1973. 40 Dutch guilders.

Professor Gindel is well known for his unorthodox views, especially those concerning the water relations of trees in arid climates. This book summarizes his experimental evidence collected over several years in Israel which has led him to believe that only indigenous or naturally domesticated trees can become completely adapted, both morphologically and physiologically, to drought. He claims that during dry periods, most of the xerophyte's water requirements are met by the absorption of mist and dew and that in order to facilitate this, the stomata open more during the night than during the day. A further adaptation to increase absorption is the greater number of stomata developed in the upper epidermis of the leaves during the dry season. As a result, despite the lack of soil moisture, the leaves remain fully turgid and because there is less demand on soil moisture, the moisture content of the soil beneath forests stands is greater than that in the open. He argues that transpiration is a physiological process reflecting metabolic activity and is therefore not subject to the physical laws governing evaporation.

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