Tropical ecology and physical edaphology

Tropical ecology and physical edaphology

TREE vol. 3, no. 5, May 79% wopm Agriculture Tropical Ecology and Physical Edaphology by Rattan Lal, John Wiley & Sons, 7987. f72.50 (xii + 732 pages...

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TREE vol. 3, no. 5, May 79%

wopm Agriculture Tropical Ecology and Physical Edaphology by Rattan Lal, John Wiley & Sons, 7987. f72.50 (xii + 732 pages) ISBN 0 47190815 0 The ecology of the tropics has received comparatively little attention in standard ecology textbooks compared to that of temperate regions1,2. A recent texts reviewed in TREE4 succeeded in redressing this balance somewhat. The title of Rattan Lal’s book suggests a further attempt to redress the balance, with an emphasis on the importance of soil properties. This is misleading: it is not a textbook and neither does it attempt to cover the whole subject of tropical ecology. In fact, its stated aim is to provide ‘a state-of-the-art review of the properties, potential and constraints of some major agroecological regions of the tropics’ and to emphasize ‘soil physical properties under natural conditions, effects of vegetation and soil fauna, and alteration by Man’s intervention’. The book is written entirely within an agricultural context and concentrates on sub-Saharan Africa. As a source of reference within this subject it is an immense and useful piece of work; as a textbook it comunfavourably with other pares [email protected]+c. The book has four parts. Part 1, ‘Tropical ecology’, includes an introductory chapter and chapters on tropical climate, rainfall, vegetation and soil, soil physical properties and variation in soil physical properties. Part 2, ‘Ecological factors and soil physical properties’, contains chapters on vegetation and soil (dealing only with forests), a general chapter on soil fauna and flora and chapters specifically with earthdealing worms, termites and ants. Part 3, ‘Man as an ecological factor’, begins with a very short introductory chapter, followed by chapters on fire, conversion of tropical rainforest (concentrating on deforestation by man), tillage, and farming systems. The final part is a brief comment on the future of tropical agriculture. Lal is a soil physicist and the sections on soil properties and their modification under agriculture have an air of authority, albeit partly generated through the use of technical terms which will be unfamiliar to a biologist. However, as might be surmized from the contents list, there is considerable repetition and overlap in this area, perhaps inevitable when one writes a series of self-contained reviews of closelyrelated subjects, but rather unnecessary in a book such as this. 120

The sections dealing with soil fauna (the only animals discussed in the book) are by contrast simplistic and reveal only a superficial understanding. For instance, the chapter on termites concentrates almost exclusively on mound-building species and the differences in physical and chemical properties between the mound soil and the surrounding area. In terms of termites’ effects on soils, this bias reflects the state of our knowledge, but mound-building termites constitute only about 5% of all termite species and there are vast areas of the tropics with no termite mounds. Lee and Wood’s book7, although published in 1971, still provides a more authoritative and balanced review of the subject. Important work on the changes in species constitution of termite faunas following cultivation8 is not mentioned: monocropping for year after year leads to a decrease in termite species harmless to crops and an increase in pest species, just as it does where other pests are concernedg; the implications for tropical farmers are clear. Lal rightly directs the reader to Lee’s recent reviewlo for an account of the ecology of earthworms and their relationships with the soil. Symptomatic of the poor quality of these sections is the abbreviation of generic names to an initial without their previous mention, and the use italics where inappropriate of (names of subfamilies and sometimes of higher taxa). The book is appallingly produced. I have never seen half as many misprints in any book I have ever read. I counted 13 errors in a single table! Many of the errors are in the specific names of animals and names of higher taxa, but there are numerous others. The reference lists at the end of each chapter omit references cited in the text and include others not cited; and citations in the text are sometimes to the wrong reference. Figures are referred to without adequate explanation; many are used uncritically; and the photographs are of poor quality. New Guinea is apparently in Africa (p. 287)! And in places the English is poor. Despite these considerable failings, the book takes a balanced attitude to the problems of destruction of tropical forests and of erosion, under the assumption that food production in the tropics must be increased. ‘Emotional’ polemic from conservationists is decried, and a call for more sound scientific data is made. Lal argues that until such data are available, ‘gradual development For effective utilization rather than

rapid mass-scale transformation’ should be our approach to deforestation; savanna agriculture should make more use of mulch farming, including reduced tillage and planted fallows to provide soil cover, and should improve traditional mixed cropping and crop rotation systems, perhaps by incorporating woody and herbaceous perennials in association with seasonal annuals (‘agroforestry’) and by integrating livestock with seasonal and perennial crops. No mention is made, however, of over-grazing and its importance in desertification. The criterion set throughout the book is to provide a better understanding of soils and how to manipulate them in order that tropical food production should be increased. There is no mention of the need to conserve tropical forest, or any other habitat, in order to protect endangered species of plants and animals, or indeed simply to maintain the diversity which makes our planet so interesting. Perhaps Lal considers this a luxury we can no longer afford. At its advertized price, this book may also be a luxury individuals cannot afford. However, it should find its place in libraries and be consulted by soil scientists, ecologists and biologists interested in tropical agriculture.

Robert H. Cowie Overseas Development Natural ResourcesInstitute, CollegeHouse,Wrights Lane,LondonW8 5SJ, UK.

References 1 Begon, M., Harper, J.L. and Townsend, CR. (1986) Ecology: Individuals, Populations andCommunities, Blackwell

2 Krebs. C.J. (1985) Ecoloav: The Experimental Analysis ofldistribution and Abundance, (2nd edn), Harper and Row 3 Deshmukh, 1. (1986) Ecologyand Tropical Biology, Blackwell 4 Sugden, A.M. (1986) Trends Ecol. Evol. 1,111 5 Norman, M.J.T., Pearson, C.J. and Searle. P.G.E. (19841 The Ecoloav of Tropical Food Crops, Cambridge University Press 6 Sanchez, P.A. (1976) Properties and Management of Soils in the Tropics, John Wiley 7 Lee, K.E. and Wood, T.G. (1971) Termites andsoils, Academic Press 8 Wood, T.G., Johnson, R.A. and Ohiagu, C.E. (19771 Geo-Eco-Trop, 1,139148 9 Metcalf, R.L. and Luckmann, W.H. (1982) lnrroduction ro insect Pest Management, (2nd edn), John Wiley 10 Lee, K.E. (1985) Earthworms, Their Ecology and Relationships with Soils and Land Use, Academic Press