Exploitation of Environmental Heterogeneity by Plants: Ecophysiological Processes Above- and Belowground

Ecology, Jan, 1995 by Kate Lajtha

There are 14 chapters, of which five deal directly with heterogeneity in light as a resource and five discuss heterogeneity in soil resources. Grime (Chapter 1) begins the book with a compelling discussion of the danger of formulating ecological theory without taking into account spatial and temporal patchiness, especially in highly fertile environments, and offers a challenge to the resource-ratio hypothesis. Baldocchi and Collineau (Chapter 2) begin the light sequence with a detailed discussion of measurement techniques and sampling problems, and offer models of radiation transfer and probability statistics for descriptions of light transfer through canopies. Indeed, one strength of this book is that each section begins with a chapter that focuses strongly on methods and problems of sampling and/or analysis. Other chapters review mechanisms of light harvesting by sun and shade leaves, costs and benefits of light acclimation, sunflecks as a patchy resource in space and time, and seed responses to gaps and light patches. Although much of this work has been reviewed before, these chapters form a thorough summary and compilation of information.

Robertson and Gross (Chapter 8) describe the potential applications of geostatistics for detecting and quantifying spatial variation in soils, a topic that the senior author has championed. Stark (Chapter 9) offers a basic review of the causes of variation in soil nutrient resources, and the following chapters offer insights into the flexibility of root architecture in exploiting different patches, changes in physiological uptake capacity in response to fertile microsites, and acquisition of nutrients from patches and pulses.

One of the greatest strengths of the book is the common focus on phenotypic and physiological plasticity among chapters; both differences among species and differences among different components of individual plants are discussed, often with insight into community-level implications. The last chapter (Chapter 14) by Bell and Lechowicz offers a discussion of plasticity from the genetic and physiological perspective that should be read by those interested in both above- and belowground dynamics. There appears, however, to be little emphasis on patchiness at larger scales or over longer time periods, with little focus on whole-system level effects on more local patchiness. This may be a conscious effort not to duplicate the Pickett and White volume, or it may simply reflect the population and ecophysiological focus of the authors. In addition, several authors focus more on summarizing research within their own lab groups than on writing a comprehensive review of the field. While this gives a concise and complete story of a particular research line, it potentially makes many chapters less useful to graduate students entering the field. Similarly, most chapters deal with variability of only one single environmental factor at a time. However, one striking exception is the review by Bazzaz and Wayne (Chapter 13) of their patch dynamics research in the Harvard Forest, which deals with the interplay of light, nitrogen, and C[O.sub.2] pulses in time and space.

Overall, the depth of detail on methods and the emphasis on theory makes this volume a very thorough summary of research on plant response to environmental heterogeneity. Most scientists will benefit from at least skimming over the entire book, although the integrative chapters should certainly be read by advanced graduate students and researchers in either field.

KATE LAJTHA OREGON STATE UNIVERSITY Department of Botany and Plant Pathology Corvallis, Oregon 97331