Published online 24 August 2006
Published in Vadose Zone J 5:1065 (2006)
DOI: 10.2136/vzj2006.0053br
© 2006 Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
BOOK REVIEWS
Dryland Ecohydrology
P. D'ODORICO AND A. PORPORATO (ed.) Springer, Dordrecht, The Netherlands. Soft cover, 341 pp. $69.95. ISBN 1-4020-4261-2.
This very timely compilation of manuscripts is focused on the relatively new scientific field of ecohydrology. As quoted by the editors of this volume, Rodriguez-Iturbe (2000) defined ecohydrology as "the science which seeks to describe the hydrologic mechanisms that underlie ecologic patterns and processes." Ecohydrology uses a multidisciplinary approach which links together dynamics of climate, water, vegetation, and soil. The framework allows these linked processes to be studied as an integrated system, thus aiding in our understanding of how alterations to the physical environment (e.g., climate change, soil disturbance) could affect the system response (e.g., water availability, plant coverage).
Ecohydrology is a very popular and important subject in the ecological sciences, but one in which vadose zone hydrology plays a vital role. Ecohydrology may simply be a buzzword, but it is quickly being used in the peer-reviewed literature. Consider Fig. 1
, the data for which was generated using a very simple search in the ISI Web of Knowledge (Thomson Scientific, Philadelphia, PA). In this simple example, the search criteria shown in the legend matches keywords generated either by the authors, "keyword plus," or contained in the abstract itself. The results show a large increase in the number of papers that relate to ecohydrology in general (more than 40+ in 2005 alone), and a more recent increase in contributions when ecohydrology is used in conjunction with "arid." If we can agree that scientific interest is correlated to emphases in the publication record, then ecohydrology is becoming a more important field of study.
The book is subdivided into four major sections: Fundamental Processes and Interactions in the Soil–Climate–Vegetation System, Hydrogeomorphology of Arid and Semiarid Landscapes, Ecohydrologic Controls on Nutrient Cycling, and Disturbances and Patterns in Arid and Semiarid Ecosystems. In Section I, the contributors discuss water flow through the soil, root zone, and xylem. The discussions presented range from general background on plant physiology in arid settings, to traditional approaches (i.e., Richards' equation with sources–sinks) used to describe water flow, to the discussion of a generalized framework that relates the physical system to water movement and water balance. In Section II, the discussions shift to hydrogeomorphology, and the interactions between landscapes and ecological function. This section has perhaps the greatest diversity of subject areas, which include large-scale (temporal and spatial) soil moisture patterns, hydroclimatology of wind erosion, and the impacts of hydrogeomorphology on riparian vegetation. In Section III, the contributors provide research on nutrient cycling and the interactions between climate states and vadose zone hydrology. The chapters in this section relate well together. Here, the readers are treated to chapters on carbon and nitrogen cycling; the influence of water status on net primary production in grasslands, shrublands, and dry tropical forests; and NOx emissions from semiarid landscapes. Finally, Section IV focuses on the role of land disturbance on ecosystem function, and how disturbance can shift species dominance. Disturbance here is broadly applied, ranging in effects from fire to overgrazing to bioturbation from termites.
The diversity of the subject areas treated in this single book is quite amazing. Of course, the challenge is to present the material generally enough for readers new to the subject to understand, but in enough detail to describe research findings that challenge the reader. The authors do an excellent job at trying to balance both goals; most provided introductory sections with copious citations and then followed with site specific examples or frameworks. The diversity illustrates the range in contributions that soil scientists, soil physicists, and vadose zone hydrologists can make in this multidisciplinary science. Also, the book calls on authors worldwide as contributors, lending itself to a very refreshing international perspective on the research being conducted in arid areas of Africa and Australia, as well as the United States.
From a personal perspective, I generally find that textbooks published as a compilation of papers to be less useful than a textbook written by a single (or a few) authors. Compilations can more easily suffer from uneven formatting, writing, parameter usage, etc. Individual chapters tend to be narrower in focus. Without special care, the goals of the chapter get choppy, the text loses its flow, and the balance between theory and application becomes uneven. In this case, however, the authors have done a good job in linking together the subject matter and in unifying the formatting and tone; often, the reader is pointed to specific chapters that provide more detailed information on related subjects. For example, in Chapter 3, the authors refer the reader to different chapters more than a dozen times. This cross-referencing is very useful because it links together the technical areas, much the way that ecohydrology itself links together many disparate subjects into a single framework. Readers who want a detailed discussion of arid and semiarid ecohydrology may find a traditional textbook more useful. However, for those who want a taste of the diversity of dryland processes and the role that vadose zone hydrology plays in those processes, this may be the book for you. I read the book almost cover to cover and found many areas where vadose zone hydrology plays an important, if not vital, role. I highly recommend it for those seeking to use vadose zone hydrology to address issues other than traditional water flow and solute transport problems.
Michael Young
Desert Research Inst., Hydrologic Sciences Division, 755 E. Flamingo Rd., Las Vegas, NV 89119
(michael.young{at}dri.edu)
