Annals of Botany 89: 499-500, 2002
© 2002 Annals of Botany Company
Stable isotope techniques in the study of biological processes and functioning of ecosystems. Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.
Stable isotope techniques in the study of biological processes and functioning of ecosystems.
Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.
Dordrecht: Kluwer Academic Publishers. £74 (hardback). 289 pp.
Publishers nowadays seem more diffident about agreeing to publish conference proceedings than was the case a few years ago. I am very glad that Kluwer Academic Publishers saw fit to publish the outcome of the stable isotopes in field biology workshop held in Perth, Western Australia, in February 1999. The workshop was held under the auspices of the Cooperative Research Centre for Legumes in Mediterranean Agriculture (CLIMA 1992–2000) with support from CLIMA, the Grains Research and Development Corporation and The Crawford Fund for International Agricultural Research.
The workshop aimed to ‘provide practical tools and experiences for researchers and students concerned with how one goes about using stable isotopes in field investigations’. The symposium, and the book, largely reflect expertise carried within Australia, a country that has been, and that remains, a major player in the application of stable isotope techniques to field-based investigations. This accounts for the predominance of Australian examples of the techniques used, and outcomes of the use of stable isotopes in field studies. The first chapter, which introduces basic concepts in stable isotope chemistry, is the only one that involves a senior author not based in Australia. The next three chapters deal with the investigation of water use by plants using natural abundance and enrichment isotope techniques and the stable isotopes of carbon, hydrogen and oxygen.
The succeeding three chapters deal with the acquisition and metabolism of nitrogen by plants in the context of natural habitats, and of agroecosystems. Most of these studies involve the natural abundance of stable isotopes, but some involve 15N enrichment. There follow three chapters discussing the use of applied (enrichment) 13C and 15N to investigate the fate of metabolites in crop plants and their soil environment. These nine chapters illustrate the use of stable isotope techniques with plants in terrestrial environments, and in some cases with phenomena and organisms that are unique to terrestrial habitats (e.g. transpiration; cultivated higher plants). The final two chapters deal with marine habitats, one with food webs in coastal habitats, and the other with 
13C as an indicator of palaeoenvironment. Chapters 2–11 all contain new experimental data, and many of them include new techniques of measurement and interpretation.
The book very generally succeeds in its stated objective of providing a practical guide to the application of stable isotope techniques in the field and the laboratory to plant (sensu lato) environmental biology. The extent of practical detail given in the various chapters varies considerably, as does the theoretical background and the extent of discussion of the interpretation of results. There are a few gnomic statements, for example (p. 11) ‘stable isotope discrimination is therefore defined as enzyme-mediated fractionation’.
The measurements and their interpretation in Chapters 2–12 are, in general, critically assessed. Chapter 3, by Pate, provides an excellent and critical review of the use of 13C in estimating water use efficiency. Pate extends the important recent innovations in his laboratory, using a range of sites of measurement of 13C within trees, including growing points and phloem sap as well as mature leaves and annual rings. The next two chapters, by Turner and by Farrington and Gailitis, deal with the use of stable isotopes (especially of hydrogen) in determining the source of water for plants and how water behaves in plants using natural abundance and tracer methodology.
The next three chapters touch on the vexed question of the interpretation of plant 15N measurements as an indication of the nitrogen source(s) for the plant. Stewart, in particular (Chapter 5), shows how the N source for plants in the natural (non-agricultural) environment can be derived from their 15N values, but rightly emphasizes that such arguments can only be used in well-circumscribed conditions. Such conditions are not widely found in nature. The other two chapters on nitrogen, by Unkovich and Pate and by Peoples, Palmer and Boddey, deal with stable isotopes in the context of the extent of diazotrophy in crops of, respectively, annual and perennial legumes. Peoples et al. deal with enrichment as well as natural abundance studies, and give a good critical account of the problems with the supply of labelled N to soil. Great care is clearly needed in using 15N measurements in the determination of the extent of diazotrophy even in managed environments.
Chapter 8 (Palta) deals with innovative experimental approaches to feeding 13C as 13CO2 and 15N and 15N-urea as a means of probing source–sink interactions in crop plants as a function of environmental conditions. Fillery and Recous (Chapter 9) discuss the use of enriched 15N sources to study (mainly) microbial processes in the nitrogen cycle in soil, concentrating on the quantity and timing of N losses after fertilizer addition and, using 15N dilution techniques, the rates of ammonification, nitrification and immobilization. Chapter 10 (McNeill) gives an excellent account of how 13C- and 15N-labelled plant material can be used in studying the accumulation and decomposition of soil organic matter.
The last two chapters deal with aquatic (mainly marine) habitats, and CLIMA is to be congratulated on extending their workshop to include aquatic environments and the palaeogeochemical perspective. Chapter 11 (Smit) provides a very thoughtful perspective on how nutrient sources can be identified in marine ecosystems using 13C and 15N, with new data from a West Australian seagrass habitat, and a clear explanation of mixing models for the analysis of the results. The final chapter (Grice) gives a wide-ranging and critical account of the use of 13C as an indicator of aquatic, and especially marine, palaeoenvironments, emphasizing the role of single molecular species natural abundance studies to give taxonomic precision to the interpretations.
In my view a deficiency of the book as a whole is that it lacks a glossary defining commonly used terms to ensure that all of the people using this volume in the laboratory or field are absolutely clear about the definition of the terms used. A further problem is that despite the emphasis on critical analyses of methodology, the occasional reference occurs to literature values of (for example) inorganic N sources without an analysis of the appropriateness of the techniques used, especially in view of recent advances (Johnston et al., 1999). Perhaps what I am suggesting here is subsumed by the encouragement in the Preface to ‘question and refine the applications and approaches detailed in the book’. I also feel that it would have been helpful if earlier prominence had been given in the book to ‘Fretwell’s Law’, cited by Smit in Chapter 11. ‘Fretwell’s Law’ points out the need for complementary data inputs from other means of investigating a plant or an ecosystem to moderate, and add to, data obtained from (the natural abundance of) stable isotopes.
A final point concerns the absence of ‘Acknowledge ments’ from the individual contributions. This does not seem to be a Kluwer house rule for conference proceedings, and the absence of acknowledgements deprives the author(s) of the means of recognizing their technical assistants, their intellectual mentors and advisers and their means of funding.
These perceived deficiencies are much more than offset by the breadth, criticality and immediacy of this attractively produced volume, which has very few typographical errors, e.g. –5 for 10–5 on p. 13. I found it to be an inspiration, and it certainly complements rather than competes with other recently published volumes on the use of stable isotope techniques in environmental plant biology. At £74 it is not inexpensive, but it still represents good value for money.
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LITERATURE CITED
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Johnston AM, Scrimgeour CM, Henry MO, Handley LL. 1999. Isolation of No3-N as 1-phenylazo-2-naphthol (Sudan 1) for measurements of delta N-15. Rapid Communications in Mass Spectrometry 13: 1531–1534.[Medline]
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