Dendroecology: principles and practice

Abstract

Trees are long-lived organisms that are influenced by both their biotic and abiotic environments. Dendrochronology can be characterised as the study of trees to provide information about past environments. Dendrochronologists have been using tree rings to understand how the environment has varied at annual, decadal and centennial scales for almost a century. Dendrochronology has provided the foundation for insights into climate variability, forest stand development patterns, and the impacts of fires, insects, windstorms and other disturbances. The science of tree rings has advanced rapidly and become diversified over the past half-century. This has included, but not been limited to, complex timeseries analyses, isotope and wood properties analyses, processbased modelling of xylogenesis, and ecosystem-level experiments. As such, the arrival of a new book on the study of tree rings is always of interest. In Dendroecology: principles and practice, Richard Phipps and Thomas Yanosky provide an introduction to the dendrochronological techniques available to study environmental history, as recorded in trees. The book begins with a very brief overview of the history of dendrochronology (in the US only), tree structure and different types of wood structure. It then outlines the basics of sample collection and issues to consider in the field, followed by a description of the crucial processes of crossdating and the standardisation of tree-ring series. Chapters 4–7 present information about, and examples of, how tree rings can assist in understanding past environmental events. Finally, Chapter 8 briefly discusses the use of tree rings in climate studies. The authors lean almost exclusively on their experience with the angiosperm species of the eastern US, and they provide a number of interesting anecdotal studies to demonstrate the application of basic principles. They especially emphasise the use of basal area increment (BAI) in their studies. Overall, I found the book disappointing for several reasons. First, given the title, I expected a stronger emphasis on the ecological aspects of dendrochronology and the integration of a far broader range of studies conducted in North America, South America and Asia that have emerged in the past 20–30 years. Second, much of the information in the book is outdated, and in some instances it is dangerously primitive. For example, any discussion of standardisation—the statistical process used to remove non-climatic information from tree rings— should acknowledge regional curve standardisation (and its variations) and signal-free standardisation, two major developments in the quantitative analysis of tree-ring time series since the mid-1990s. The seminal works of Keith Briffa, Tom Melvin, Jan Esper and Ed Cook (e.g. Cook & Kariukstis 1990; Melvin & Briffa 2008; Esper et al. 2010; Briffa et al. 2013) are easily accessible, and yet reference to them is almost entirely missing from this volume. Several other commonly used standardisation methods may be more appropriate to use in certain circumstances than that advanced by the authors, but the authors make no mention of these. Further, key technical issues with standardisation, such as the use of residuals rather than ratios (the authors only point to the use of ratios for standardisation), were raised in the late 1990s by Cook and Peters (1997). Anyone attempting to work with tree-ring time series needs to be aware of these issues. In addition to omitting key advances, the authors introduce opacity to basic terms such as standardisation and smoothing that have different purposes. This is likely to confuse readers, especiall students of dendrochronology. A further case in point concerning the dated nature of the book is its reference to Henri Grissino-Mayer’s ultimate tree-ring webpages, which have been defunct for some time. Third, the writing is repetitive and confusing. For example, BAI, and its calculation, is ‘introduced’ at least three times. In general, the text wanders back and forth throughout the book, making a clear reading of the important points difficult, especially for a dendrochronological novice. Extensive use of phases such as, ‘. . . as discussed in the previous section . . .’ or ‘. . . as will be discussed in the next section . . .’ followed by a re-iteration of what was/is discussed above/below, muddy the text. An odd quirk is the ‘selected references’ at the end of each chapter and little in-text referencing, which makes it difficult for a reader to follow up on any specific points of interest. Finally, an explicit statement about the geographical context of the book would have been useful. With the dominance in the literature of dendroecological studies using coniferous species, the authors could have leveraged their experience in angiosperm forests in the eastern US to their advantage. Had they done so, and made a much more rigorous effort to discuss a broader range of ecological studies, this book would have represented a valuable contribution to the literature. However, novice dendrochronologists would be better directed to Jim Speer’s Fundamentals of tree-ring research (Speers 2010) as an introductory text. Students who want a more detailed and extensive reference to the types of environmental disturbance signals that may be recorded in trees could consult Fritz Schweingruber’s Tree rings and environment dendroecology (Schweingruber 1996). For those interested in the latest advances—conceptual, technical, and geographical—in dendroecology, the recent Dendroecology: tree-ring analyses applied to ecological studies, edited by Mariano Amoroso and colleagues (2017), would be a much better point of departure.