European Forests and Global Change

Abstract

P. G. Jarvis (1998) Pp xviii + 380. Cambridge University Press. ?60·00 (hardback), ISBN 0-521-58478-7. This book is a synthesis of the 2-year EU-funded project ‘European Collaboration on CO2 Responses Applied to Forests and Trees’ (ECOCRAFT), starting in 1993 with 13 participants from nine countries. The aim of the project was to describe growth processes in different tree species as affected by raised CO2 levels and increased temperature, and to model these responses, including biochemical and physiological processes. The models were intended to be up-scaled to stand level and checked out in field experiments and on a longer time scale. Paul G. Jarvis was the leader of the project and the editor of the book. The book consists of 10 chapters, describing different aspects of the project, on various tree species and carried out by different techniques, plus a concluding chapter. Trees were grown in open-top or closed-top chambers, at different levels of CO2 and temperature control, and with different nutrient and watering regimes. In addition, field-grown trees were studied by the so-called branch bag technique, where growth, photosynthesis and carbon balance is studied on single branches in closed chambers. The large variation in methods and species used is, in my view, a major problem with the study, and has made it difficult to make comparisons between experiments. Each technique has its advantages and disadvantages. By growing trees in chambers, for example, growth and carbon balance can be studied in relation to environmental variables under semi-controlled conditions, but controls outside the chambers are needed to correct for the ‘chamber effect’ on temperature and light levels. By using the branch bag technique this problem is avoided but, on the other hand, missing sink control may be another problem. The branch bag technique should only be used for studies on CO2 exchange rates, not for carbon allocation studies. This disadvantage is to some degree also admitted in the book. In the various chapters of this book, some aspects of the study are thoroughly described, whilst other descriptions are more superficial. In the chapters on photosynthesis and respiration, more emphasis could have been placed on the physiological meaning of the down-regulation of photosynthesis found at raised CO2 levels, otherwise the chapter is informative and good. The chapter about bud and growth phenology also contains useful information, in particular for the selection of species and provenances for a possible future global change. The description of the CO2 responses on biomass, growth and carbon allocation is very informative, and the effects of varying nutrient level on long and short-term responses are clearly pointed out. Similarly, the effects of raised CO2 level on stomatal conductance and water use efficiency in Mediterranean as well as in temperate and boreal tree species are well described. In one chapter the interaction between the CO2 and nutrient level on different species is shown, and the advantages and disadvantages of the Ingestad method for growth balanced nutrient addition are described. The chapter on interactions between temperature and CO2 is also very informative, and adds new knowledge about temperature responses on physiological processes at different CO2 levels. However, in this chapter, studies of the CO2 and temperature effects on photorespiration rates are missing; this is, in my view, another major problem with the book. In another chapter, attempts are made to upscale the results from single tree measurements to stand level, but more emphasis should have been placed on this part, and on verifying the models used to predict future changes in temperate and boreal forests. Therefore, the predictions are somewhat incomplete and speculative. In the last concluding chapter this type of weakness is also admitted, as well as the need for more studies on the effect of tree age on the responses, fluxes of water and CO2 in the field, nitrogen deposition maps and further studies on the CO2 and temperature effects on water use efficiency. The book is a useful, but not complete, supplement to previous books and papers on this and similar topics, e.g. Rozema et al. (1993), Eamus & Jarvis (1989), Apps et al. (1995), Amthor (1989) and Long & Woodward (1988). It contains information about global change responses in some economically important species, e.g. sitka and Norway spruce, birch, beech, poplar, chestnut and cherry, and will undoubtedly be of great benefit for foresters throughout Europe. The book may be considered a valuable and relevant supplement to the literature on global change responses, and useful for applied ecologists, forest researchers and teachers as well as people working in public administration and management at different levels throughout the northern hemisphere.