Annals of Botany 91: 501-502, 2003
© 2003 Annals of Botany Company
Karnosky, D.F., Ceulemans, R., Scarascia-Mugnozza, G.E., Innes, J.L., (eds.) The impact of carbon dioxide and other greenhouse gases on forest ecosystems. IUFRO Research Series 8
The impact of carbon dioxide and other greenhouse gases on forest ecosystems. IUFRO Research Series 8.
Karnosky DF, Ceulemans R, Scarascia-Mugnozza GE, Innes JL, eds. 2001.
Wallingford and New York: CABI Publishing.
£55 (hardback). 357 pp.
This book is the eighth in a series of monographs published by CABI in association with the International Union of Forestry Research Organisations (IUFRO), and is the third report of the IUFRO Task Force on Environmental Change. The report has been compiled by an impressive array of editors, and comprises 11 chapters written by a total of 28 authors, drawn from a range of recent experimental projects in Europe and North America. The book must therefore be regarded as an authoritative statement on what we know about the impacts of greenhouse gases on forests.
The first and final chapters, written by the editors, summarize where we have got to and the significant gaps that remain in our knowledge. The nine chapters comprising the meat in this sandwich primarily address the impacts of elevated concentrations of carbon dioxide (CO2) on gas exchange (i.e. photosynthesis, respiration and stomatal conductance), above-ground growth, root and mycorrhizal growth and function, phenology, soil respiration and nutrient cycling. In one lengthy, notable chapter, interactions between elevated CO2 and ozone (O3) on anti-oxidants and foliar defence compounds are treated in detail, and a further short chapter treats interactions more widely. Throughout the book, however, the subject of interactions between CO2 and nitrogen supply, whether as deposition, fertilizer or mineralization, comes up repeatedly. Integration and extrapolation are treated through the use of models in one chapter in particular, but they also crop up in several other chapters as part of the normal scientific method (as they should!). Experimental methodology and approaches are mentioned in individual chapters in passing, where they are adequately supported by references, but there is one chapter explicitly devoted to the use of FACE (Free Air Carbon dioxide Exposure) systems for studying the impacts of greenhouse gases on forest ecosystems.
The main emphasis is on CO2 and, to a lesser extent, O3. Regrettably, the other important greenhouse gases that occur both naturally and through anthropogenic actions, and which are rising in atmospheric concentration, nitrous oxide (N2O) and methane (CH4), are treated in passing to a much lesser extent. There is a common perception that despite their high rates of increase, these greenhouse gases are of low importance because of their very low concentrations in the atmosphere. The global warming potentials (the time-integrated warming effect of a unit mass of the gas in today’s atmosphere relative to that of CO2) of CH4 and N2O based on their present concentrations and time-integrated over 100 years are 23 and 296, respectively, but if integrated over 20 years are 62 and 275, respectively (Watson et al., 2001). Thus, if we consider time scales of relevance to the period over which we can comfortably continue to burn fossil fuels, the rising concentration of atmospheric methane is a much more significant component of climate change than has been appreciated. Given the title of the book, one could have expected these greenhouse gases to have been given much greater prominence.
The main emphasis of the book is on the interactions between greenhouse gases and processes in forests and, consequently, this book should be of great value to all who are trying to understand how changes in the atmosphere may affect forests and how forests may influence the composition of the atmosphere. These are questions of considerable interest and concern, particularly because global forests removed almost 40 % of the anthropogenic emissions of CO2 from the atmosphere during the 1990s. How this was done, what drives and what regulates the processes, and how long forests will continue to be effective in this way all remain key questions affecting our future. Interest in these questions really began in a big way in 1987, and since then there has been a huge proliferation of relevant literature. The chapters in this book attempt a summary of the work on these questions over the past 15 years, with varying degrees of bias and success, and provide a rich reservoir of relevant literature. Without doubt, this book will be useful to all tangling with these issues.
LITERATURE CITED
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Watson RT et al. (eds) 2001. IPCC third assessment report: climate change 2001. Synthesis report. Geneva: IPCC.
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