Pp. xviii+380. Cambridge University Press, Cambridge. ISBN 0-521-58478-7. Price £60 (hardback).
Investigations on the effects of CO2 enrichment on plants are dominated by results from herbaceous species. Experiments on trees have generally been confined to seedlings or small saplings. Yet the longevity of trees and their capacity to sequester anthropogenic carbon makes them the critical life form for considering natural methods of CO2 abatement. Therefore, the expansion of experiments on trees is important, a fact which has filtered down to enhance the development of CO2 fumigation techniques for tall saplings, trees and patches of forests. This volume is therefore topical and novel as it presents new and extensive sets of data on the responses of different forest trees to CO2 enrichment and temperature increases. The data were accumulated in a European-scale project and the volume describes a logical way forward to providing a mechanistic understanding of how forests will respond to probable future increases in CO2 and temperature. The approach is to start with the responses of organelles and individual small plants and scale up to communities of small to moderate sized individuals and then apply what is known at these scales to models of patch and forest responses. What is then needed is a method for testing the model projections and this can be done against measurements of, for example, CO2 and water vapour exchange by the eddy covariance technique. These measurements are available in a sister project to the one initiating this volume; unfortunately, the data are not presented in this volume.
There is much hard science in this book, together with considerable information on the responses of 10 species of tree grown through Europe. The members of this project work in nine different European countries from a northern latitude of 63°N southwards to 42°N and this, in the fashion of typical European Union-funded projects, provides a large range of different climates for investigating impacts on CO2 responses. The volume is most unusual in that data are presented in the open market, rather than in the often hidden volumes produced by the European Union. This is a brave and I believe successful endeavour.
There are 11 chapters, 10 of which provide up-to-date information on methods for CO2 fumigation of quite tall individuals (up to 7.8 m), and on the species-specific responses of photosynthesis, respiration, growth and water loss to changes in CO2, temperature and nutrient and water supply. In 1990 Jarvis (P.G. Jarvis, personal communication, Ascot Station) indicated that plant responses to CO2 enrichment were just a matter of speeding up the growth process and this is still generally true, perhaps now more tightly defined as compressing ontogeny. However, many other features have now come to the fore, such as stomatal responses (both morphological and functional) and acclimatory physiology. In addition, the majority of the work on herbaceous species suggests little response of canopy leaf area index to CO2, as a consequence of improved water use efficiency. However, the work on tree species has shown what modellers had demonstrated for some time, that leaf area index can increase under CO2 enrichment.
As for the bottom line, what will happen to European Forest in the future, then the last chapter pulls together the various and species-specific responses to provide six or seven highly probable growth and physiological responses. However, there is a real undercurrent which suggests that species differences are large and, at least for multi-species forests, this may exert future changes in community membership – but this is not the scope of this interesting and data-rich volume.