296 BOOK REVIEWS

webs. This is the largest chapter of the book in which one finds six papers. The first paper is devoted to an interesting discussion of how a part of the theory relevant to this book has emerged. The second paper is devoted to models of aggregate data. Here one finds models of anarchy (random food webs), models with no cycles and the analysis of a special, but important case of the cascade model. In the next paper the cascade model is tested on individual community webs. The fourth paper compares predicted to ob- served lengths of food chains. It is followed by a theory of food chain in large webs. The last paper is about trophic niche overlap.

Chapter 4 contains binary matrices on 113 community food webs. The book presents new and important results about the structure of

community food webs derived from a collection of directed graphs. Re- views of research that led to this study, analyses, results and discussions give the reader a thoroughful view of progress that has been made in theoretical ecology regarding community food web structure.

The book is a very valuable contribution to fundamentals of community ecology.

I warmly recommend this book to students and teachers of community ecology and theoretical ecology. Parts of the monograph may be taught in undergraduate courses since the laws are fundamental and elementary. Some parts in the third chapter on stochastic theory are more suitable for graduate study.

TARZAN LEGOVIC 'Rudjer BoskoL'ic' Institute

P.O. Box 1016, YU-41001 Zagreb, Yugoslavia

EPIDEMICS OF PLANT DISEASES

Epidemics of Plant Diseases: Mathematical Analysis and Modeling (2nd, completely revised edition). Jfirgen Kranz (Editor). Ecological Studies, 13. Springer, Berlin, 1990. 268 pp., DM160.00 ISBN 3-540-52116-X.

During the quarter of a century since the publication of the first edition of Epidemics of Plant Diseases: Mathematical Analysis and Modeling, there have been many developments in theoretical population biology. It has been suggested (Kareiva, 1989) that these remain unknown to most ecolo- gists, and that experimental ecology is developing almost as a separate field to theoretical ecology. In epidemiology this does not seem to be the case. Medical epidemiology continues to benefit from a dialogue between biol- ogy and mathematics (Anderson, 1991), and the second edition of Epi- demics of Plant Diseases provides evidence that the same is true of

EPIDEMICS OF PLANT D I S E A S E S 297

botanical epidemiology. Of course, both these disciplines must continually justify their existence by providing predictions that are reasonably accurate and potentially useful: so difficult that every source of help must be utilized to the full.

As might be expected, the second edition is essentially a new book. After an introductory chapter by the editor, it comprises six chapters in which different authors discuss aspects of quantitative botanical epidemiology. Their approaches vary.

Hau and Kranz (Chapter 2) review mathematical and statistical tech- niques with applications in epidemiology, and Butt and Royle (Chapter 5) give a detailed account of one of these, multiple regression analysis. The description of empirical phenomena and experimental results by mathemat- ical functions is central to modern epidemiology, and these two chapters are useful as works of reference. But in practice, we start with an epidemio- logical problem to solve rather than with an analysis in search of an application. This is the approach of Madden and Campbell (Chapter 6), who review mathematical models of disease progress curves. Here again, a useful reference work has been produced. The value of all these chapters is that they start from first principles (all three mention simple linear regres- sion analysis) and so should be accessible to any plant pathologist inter- ested in the collection and analysis of data relating to pathogen populations and their effects on host populations.

The other three chapters have a rather different feel. Their shared concern is the simulation of epidemics, or aspects of them. Jeger (Chapter 2) deals with spatial models, Gilligan (Chapter 3) with the population dynamics of soilborne pathogens, and Waggoner (Chapter 6) provides an eclectic overview of simulation modelling. None of these topics lend themselves to the step-by-step approach of the user manual, and the authors have instead provided snapshots of current research in their selected areas. By their nature, these chapters may date more quickly than the others: if so, they will have contributed to their own obsolescence by raising some of the key issues which epidemiologists will have to tackle over the next few years.

Epidemics of Plant Diseases is concerned by and large with pathogens in managed plant populations, reflecting a bias of plant pathology as a whole. However, plant pathogens are not uniquely associated with intensive farm- ing practices. The study of pathogens in natural populations is the problem facing medical epidemiology, but until recently (Burdon, 1987) has received little attention from botanical epidemiologists. This will increase as we learn to depend less on routine chemical control of crop disease, and to practise epidemiology in complex agroecosystems. Thus we must continue to attract quantitative ecologists into an area where theory and experimen-

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tation continue to develop together. Epidemics of Plant Diseases is a book which will help to do just that.

REFERENCES

Anderson, R.M., 1991. Populations and infectious diseases - ecology or epidemiology? J. Anim. Ecol., 60:1-50.

Burdon, J.J., 1987. Diseases and Plant Population Biology. Cambridge University Press, Cambridge, UK, 208 pp.

Kareiva, P., 1989. Renewing the dialogue between theory and experiments in population ecology. In: J. Roughgarden, R.M. May and S.A. Levin (Editors), Perspectives in Ecological Theory. Princeton University Press, NJ, pp. 68-88.

GARETH HUGHES School of Agriculture,

Unicersity of Edinburgh Edinburgh EH9 3JG

Scotland, UK

ECOPHYSIOLOGICAL PROCESSES OF GROWTH IN ANNUAL CROPS

Simulation of Ecophysiological Processes of Growth in Seueral Annual Crops. F.W.T. Penning de Vries, D.M. Jansen, H.F.M. ten Berge, A. Bakema. Simulation Monographs, 29. Pudoc, Wageningen, Netherlands, 1989. DfI.100/US$57. ISBN 90-220-0937-8.

Realizing early that simulation models of plant growth and crop produc- tion can provide substantial support to agricultural field research, for evaluating new sites, crops, and management techniques and for impact assessments of weather and climate, researchers at the Agricultural Uni- versity of Wageningen (foremost among them C.T. de Wit, F.W.T. Penning de Vries, H. van Keulen, and J. Goudriaan) have over many years devel- oped a reliable set of simulation models (BACROS, SUCROS, SAHEL, SAWAH etc.) which are widely applied in all parts of the world. The models are organized according to the four levels of plant production introduced by De Wit: (1) no limiting effects of water, nitrogen or phos- phate; (2) water shortage as main limiting factor; (3) nitrogen shortage as main limiting factor; (4) phosphorus shortage as main limiting factor. From one production level to the next, the complexity of the simulation model increases.

The present book deals with a coherent set of simulation models and supporting computer routines on the first two production levels (i.e. with- out nitrogen or phosphorus limitations). The programs are written in