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Book Review |
2Division of Biological Sciences, University of Montana, Missoula, Montana 59812 USA; 3Wildlife Biology, University of Montana, Missoula, Montana 59812 USA
In their new text, The Ecology of Plants, Gurevitch et al. have produced a unique and valuable resource for plant ecologists. As a tool for teaching, this book is an improvement over existing plant ecology texts, due to its comprehensive scope, its rich illustration, and the level at which material is presented. The Ecology of Plants covers ecophysiology, soils, evolution, population biology, life history, community structure and dynamics, ecosystems, landscapes, climate, biomes, paleoecology, and global change. As we present in detail below, the primary weakness of the text is its organization. However, because of its strengths, this text is in use at the University of Montana as we write and will be used by some or all of us in the future. Below we have organized our detailed comments and opinion on The Ecology of Plants by the order of the general sections used by the authors.
Gurevitch et al. begin with a short chapter on ecology as a science. This section will be appreciated by those teaching at the undergraduate level in particular. The presentation is clear, the authors do not fall into the trap of Popperian dogmatism, nor do they simply insist that ecology is more than environmentalism. Instead, we are provided with a broad perspective on scientific epistemology, the value of experimentation, and a brief history of ecology. This is a nice opening to the section that follows, although the leap from Darwin and Haeckel to John Harper left some of us wondering where Warming, Schimper, Clements, and Gleason had been placed. We found Clements and Gleason in wonderful detail in Chapter 12.
The first meaty section is the unit titled "The Individual and its Environment." This section deals with aspects of plant physiological ecology and is divided into chapters on light and photosynthesis, water relations and energy balance, and soils, mineral nutrition, and belowground interactions. Within each chapter, the authors chose a traditional descriptive approach in which a great deal of useful information is provided. However, we thought that a more contemporary approach, perhaps emphasizing how plant physiological responses under different environments relate to overall plant strategies within population, community, and ecosystem contexts might be more beneficial for students of plant ecology. Overall, there is a lack of conceptual integration in this section of the book, and the information does not always follow the most logical structure. There is also little emphasis on the integration of responses at different time (from short-term to evolutionary responses) and spatial scales (from cells to entire plant responses). The student ends up with an excellent source of ecophysiological information, but little appreciation that plants deal with numerous physiological and biophysical constraints that impose important trade-offs that prevent plants from excelling in each of their main functional outcomes (e.g., growth, stress tolerance, defense against consumers, reproduction). There is little development in this unit of the historical progression of the field, and there is insufficient reference to classical work.
Given the traditional approach taken by the authors in Part I, it is surprising that there is no stand-alone treatment of plant responses to temperature (there's a little in Chapter 22). After all, temperature and water availability are the two most influential factors on productivity and distribution. While the authors include an energy balance section within the water relations chapter, there is no mention of responses to low and high temperature. We thought that an initial section on energy would have provided a stronger general framework for the following sections on carbon, water, and nutrient relations. This organization would also emphasize the role of plants as primary drivers of energy flow within ecosystems and provide a clear tie to Parts IV and V.
Chapter 2, "Photosynthesis and the Light Environment," does not emphasize the concept that assimilated carbon is partitioned into many competing functions and that overall carbon allocation strategies have important consequences on productivity, growth rates, reproductive potential, stress tolerance, and competitive interactions. While not crucial, this omission is likely to cause physiology-challenged ecologists a little reorganizational heartburn. Without reorganization, students may not fully appreciate that overall biomass accumulation may be substantially limited by respiration costs, which in turn are regulated by growth and allocation strategies as well as the environment (e.g., temperature). A more comprehensive chapter on carbon relations would provide this perspective. As it is, the chapter quickly moves to explanations of the light and dark reactions of photosynthesis without providing an overall conceptual overview of the function of these two important phases and their interdependence from the onset. While there is substantial detail on light harvesting, the conceptual understanding of how solar energy is used to synthesize ATP in the chloroplast is not clear (Fig. 2.2 may be misleading). The dark reactions are described in one short paragraph with no mention on how the products of the light reactions are used in the dark reactions. There is no mention at this point that actual carbon "fixation" and reduction occur during this phase. This is unfortunate as it is this initial reduction by plants that allows energy transfer through trophic levels within ecosystems. The dual affinity of rubisco to CO2 and O2 and the consequent photorespiratory cycle are not brought up until the discussion on photosynthetic pathways. Adding to the organizational confusion, the chapter moves into a discussion of the effects of light and carbon uptake limitations prior to a more in-depth description of the dark reactions; these are included in an explanation of the different photosynthetic pathways. The chapter includes strong sections on evolutionary aspects of photosynthetic pathways, geographic distribution, habitat preferences, and adaptations to the light environment. However, the last section should be titled "Plant Responses" because it includes both adaptation and acclimation. The information is excellent, but we believe the chapter would be improved if the light and dark reactions in C3 plants were presented in sufficient conceptual detail first, and afterwards the chapter proceeded to the "problem" of rubisco and photorespiration in C3 plants and the evolution of alternative photosynthetic pathways with consequent costs and benefits. With this organization, the progression to the responses of plants with different pathways to light, water, and temperature, the relationship of pathways to habitat preference and geographic distribution, and general ecological strategies would flow naturally. Links between this chapter and others could be made by emphasizing the links between photosynthetic traits and plant life history traits (e.g., fast- vs. slow-growing plants, early vs. late successional species).
The chapter on water relations suffers from the same lack of integration and cohesive structure. The abundant information is often scattered (e.g., responses to flooding or drought) or missing all together (e.g., there is no mention of the concept of water-use efficiency or the importance of xylem structure in water relations). Students and instructors without strong ecophysiological backgrounds would benefit from a simple discussion of why plants lose so much water, the main compartments that water moves through in the plant (introducing here the concept of the relative role of these compartments to maintain a functional homeostasis with respect to water transport), and then a clear explanation of water potential as the driving force for water movement. In the discussion of water potential the authors make a minor but common mistake by portraying matric potential as an independent component of the total water potential. Matric potential is actually a combination of osmotic and hydrostatic pressures and should be omitted from the equation. A more linear explanation of the water potential components along the overall plant–atmosphere continuum could logically lead to an explanation of why xylem water potential is such a good indicator of overall plant water status and a variable commonly measured by plant ecologists. (Fig. 4.10 in the soil chapter would be much more relevant here.) The sections on strategies for coping with water availability are quite unorganized. The student should be provided with a clearer understanding that plants exhibit a variety of phenological, structural, anatomical, and physiological responses to variation in water availability and that these responses may operate at different times (short-term to evolutionary time scales) and spatial scales (from cells to entire plants). The "strategies" employed by plants to cope with water stress are presented more as a list and could have been divided into groups—for example, species that "avoid" any activity during water stress (drought escape) vs. plants that remain more or less active during drought (drought resistance). Perhaps it is reasonable for a general text on plant ecology to omit some important strategies for drought resistance, but increased water transport and storage tissues in woody plants and increased resistance to xylem cavitation are missing and hydraulic lift (which should probably be generalized to "hydraulic redistribution") by roots comes later in the soil chapter.
Of the three chapters in Part I, the chapter on soil and mineral nutrition is the most deficient. The chapter starts with a great deal of descriptive detail on soil composition and structure without an initial discussion of why these details are important to plants. There is no emphasis on the importance of plant mineral nutrition or its effect on functional strategies and ecosystem properties. While the chapter goes into great detail on soil properties it does not explore in a logical order the many strategies plants employ to deal with limiting nutrients (mycorrhizae and nitrogen fixation are in independent sections) and the trade-offs associated with these strategies. Not including these potential trade-offs is not crucial, but they would offer a great opportunity to link this chapter to the carbon and water relations chapters and to subsequent chapters on ecological strategies and plant–animal interactions. The chapter omits fundamental concepts such as nutrient-use efficiency, nutrient residence time (or life span), nutrient recycling, and the relationship of these traits to growth forms (e.g., a distinction between evergreen and deciduous species, etc.). There is little or no emphasis on how mineral nutrition feeds back to soil properties (including microbes) and the implications for community and ecosystem dynamics. In much the same way as we would like to see for the water relations chapter, why not start with an exploration of why mineral nutrients are needed for plant growth and how soil properties affect nutrient availability and end with a clear overview of how plants respond to variation in soil fertility and physical characteristics?
Like much of the rest of the text, the population biology section (Chapters 7–9, or 5–9 if you include the two chapters on evolution) is comprehensive, but the organization is somewhat obscure. The section begins with a general discussion of evolutionary processes (Chapters 5 and 6), followed by population growth (Chapter 7), individual growth (Chapter 8), and life history theory (Chapter 9). We agreed that for teaching plant ecology, we would almost certainly present the material in a different order than in the text—at a minimum, by putting individual growth before population growth and after evolution, which has traditionally been approached by plant ecologists from an individual perspective (for example, estimating fitness from individual survival and fecundity, rather than by projecting genotype-specific lambdas). Yet Gurevitch et al. should be commended for including chapters on evolutionary processes in their book, as these important topics are missing from many plant ecology texts. Indeed, with the growing interest among ecologists in rapid evolution and the role of evolutionary processes in plant invasions, there is ample scope for even broader coverage and integration of ecology with evolution in textbooks.
The material covered in the subsequent chapters on population biology was also presented in a somewhat haphazard manner. For example, the chapter on population growth only briefly mentions dispersal and density dependence, and almost entirely focuses on age- or stage-structured transition matrices, with an extensive discussion of matrix modeling methods, including calculation of sensitivity, elasticity, reproductive value, as well as methods for incorporating environmental stochasticity. In our experience, undergraduates would benefit from a more complete discussion of basic (i.e., unstructured) population models before moving so quickly into a detailed discussion of matrix projections. Gurevitch et al.'s emphasis may well reflect the state of the art in plant demography, but our sense is that the groundwork for this material isn't adequate. For example, there is only a brief discussion of life tables, but no real discussion of the elements of a life table or different approaches to collecting data for life tables (i.e., cohort, partial cohort, or static analyses), or how one integrates life table statistics into projection matrices. Although the authors cite a few alternative methods to transition matrices, alternative mechanisms of population growth are scattered among other chapters. For example, clonal spread is discussed in detail in Chapter 8, without reference to methods for inferring population growth and spread from clonal tillering, which is, in our opinion, an approach much more naturally suited to rhizomatous herbaceous perennials than transition matrices. Density-dependent population growth models are presented in the context of r vs. K selection in Chapter 9, but only discussed qualitatively in the population growth chapter. Metapopulation models and source–sink dynamics appear in Chapter 17 (landscape ecology), creating the impression that spatial dynamics and population dynamics describe different processes, rather than acting as ends of a continuum of population structures. Interspecific competition is presented in Chapter 10, but the relationship to density-dependent population growth is not clear from the text alone; it would need to be made by a course instructor.
Similarly, Chapter 8 combines basic plant morphology; a generalized life cycle; clonal growth, foraging, and reproduction (awkwardly split into two disjunct sections); a large section on pollination biology; and a discussion of seed dispersal and seed banks. There is no real synthesis of the different methods; e.g., comparison of "dispersal" by branching, ramets, pollen, or seeds. Neither is it clear why dispersal belongs with individual growth, rather than population growth. In the discussion of clonal growth, as in other places throughout the book, those whom we perceive as movers and shakers in the field (de Kroon and van Groenendael [1997]
, Cain [1994]
, and Alpert [1991],
for example) were not mentioned. This chapter would have been better split into three; one dealing with modularity and clonal growth, the second discussing reproduction, pollination ecology, and pollination syndromes, and the third discussing frugivory, seed dispersal, and seed predation. We found the section on the ecology of fruits and seeds in Chapter 8 particularly frustrating, as the coverage of frugivory, seed dispersal and predation, and seed dormancy was rudimentary at best, although granivory is covered in more detail in Chapter 11.
The chapter on life history (Chapter 9) includes a general discussion of life history strategies (annual vs. perennial; semelparous vs. iteroparous; seed dormancy and germination requirements), seed size vs. seed number trade-offs, phenology, and a brief section on using demographic models to quantify life history trade-offs. The demography section is a bit repetitive with Chapter 7; for example, the justification for why geometric mean population growth is the appropriate measure of fitness and long-term population growth is given in both, though in slightly different words. We believe that these sections would also be greatly improved by tighter links among chapters; for example it is almost—but not quite—clear that matrix models are central to life history theory because genotype-specific population growth rates are estimates of fitness. A brief appendix is presented to discuss simple statistics, with description of simple statistics like mean and variance, and verbal explanations of statistical tests and P values. The combination of the very basic and general appendix with the detailed section on matrix calculations in Chapter 7 seems targeted to different audiences. We were impressed by the effort to explain to readers how to do calculations for population models; it can be frustrating when texts mention that models exist and provide nifty results, but do not explain relevant calculations.
Criticisms stated, we agree that The Ecology of Plants is the text we would choose if population biology was the emphasis in an ecology course. As for other sections, our opinion was swayed by the impressive breadth of engaging material.
Following Part III, "From Populations to Communities," the text springs immediately into competition. The community context comes in Chapter 12 in a rather traditional discussion of Clements and Gleason. The chapter on competition is strong, but is missing or only perfunctorily addresses current advances in indirect interactions, allelopathy, and, to the chagrin of at least one of our reviewing crew, facilitation. Competitive hierarchies are mentioned, but the fascinating implications of nontransitive competitive webs (indirect interactions among competitors á la Thomas Miller [1994]
and Jonathan Levine [1999]
are not explored). One of us thought that this was the most serious oversight in the text. Positive interactions among plants (Callaway, 1995
) are mentioned in a later chapter in the obligatory discussion of the mechanisms driving succession, but are otherwise ignored. Allelopathy is written off in the standard manner of the 1980s with the added twist of misinterpreting a recent paper written by one of our review group (Callaway and Aschehoug, 2000
). For a general text, the sections on modeling competition are clearly written and nicely comparative, and the section on competition along abiotic gradients is up to date and excellent. This chapter may be improved moderately by incorporating classic statements by John Harper (1961)
on distinguishing competition for resources from other forms of interference.
Herbivory and pathogens are treated in the same chapter, appropriately in our opinion, and this chapter includes a short but highly effective consideration of biological control of exotic plants by insects, but with no mention of pathogens as biocontrols. The subsections in the chapter "Effects of Herbivory on the Community Level" begin with the consequences of herbivore behavior, move smartly through subsections on introduced and native herbivores and on to a too-small portion of "generality." One glaring hole in this section is the omission of a discussion on McNaughton's (1983)
classic work in Africa and on Richard Root's (1996)
work on the community impacts of herbivores feeding on goldenrod. However, the section on plant defenses is top-notch and thorough, although a clear treatment of the controversy on the costs of defense would have rounded this section out and possibly provided a tie to earlier chapters on carbon allocation. Following this are two pages on "evolutionary consequences" of herbivory that are not connected in any way to communities. Ecology teachers beware; if your goal is a clear organizational picture of plant ecology for relatively naive students, you will have to reorganize. The pathogen section is a quick mention of some cool ecological tidbits, but is not tied to the previous text on herbivory at all.
Chapter 12, on community properties, comes without apology or comment after the chapters on competition and consumers. We think that this organizational strategy could have worked, but it would have taken some clear explanation of how the stuff just digested on interactions leads in some way to the properties of communities. One approach to bridging chapters on competition and herbivory to the community properties material might have been to include a chapter explicitly dealing with food webs. Rich topics such as trophic cascades, keystone species (Power et al., 1996
), subsidies, and subsidized food webs are mostly ignored in The Ecology of Plants, and inclusion of these topics would have made for engaging reading. In this section the enormous body of work describing plant communities is limited to species richness, diversity, dominance, and basic sampling strategies—multivariate ordination and classification come four chapters later in an entirely different section, a chapter titled "Communities in Landscapes" in Part IV, "From Ecosystems to Landscapes."
Chapter 13, on succession, is standard but strong. Students will come away with a clear understanding of succession and why it is important to plant communities. Missing however, is any mention of cyclic or shifting mosaic dynamics, and the subsection on primary section follows sub-subsections on volcanoes, fire, colonization, and others, but no parallel subsection on secondary succession. This is also one of the only chapters that simply does not include enough current literature on succession.
Chapter 14 is a peach, and here Gurevitch et al. have made a significant stride in teaching ecology. By thoughtfully probing dominance, abundance, and rarity, and including theory developed by Deborah Goldberg and colleagues, David Tilman, MacArthurian distribution curves, and niche theory, this chapter in The Ecology of Plants will provide advanced students and most professors with stimulating thoughts and new directions. These concepts are blended smoothly with a following section on invasives that will no doubt help make the material more relevant to undergraduates. In our opinion, however, the treatment of invasives could have been bolstered by both a clear explanation of the natural enemies hypothesis as the primary hypothesis for invasive success and a broader inclusion of the processes driving invasion such as presented by Richard Mack and colleagues (2000)
. More generally, inclusion of neutral community theory such as that promoted by Steven Hubbell (2001)
would have fit well in the discussion of abundance and dominance.
The Ecology of Plants leaves communities and proceeds to ecosystems cleanly. "Processes" in Chapter 15 are nutrient cycling, carbon flow, and productivity, but nowhere is the movement of energy explicitly and clearly explained as a crucial ecosystem process. This chapter includes two very nice subsections on nitrogen and phosphorus in ecosystems, interrupted oddly by an equivalent subsection titled "Ecosystem Nutrient Cycling and Plant Diversity," after which puzzled readers will find processes described for other elements. A simple move of the diversity section to the end would solve the problem.
Chapter 16 probably comprises the most unusual large-scale organizational choice of all. We could find no connection between "communities in landscapes" and ecosystems. On the other hand, multivariate ordination is just skipped by many instructors, and this may be easier to do when it is hiding in an ecosystems unit. This said, The Ecology of Plants deals with the messy issues of ordination and classification quite nicely. Direct and indirect ordination are clearly contrasted, several modern techniques are presented, and this is all followed by a connection with remote sensing. This chapter is followed by a nice chapter on landscape ecology, which combines the explanation of remote techniques with island biogeography and metapopulations theory. The latter two bodies of theory link perfectly, but these were not tied to remote landscape analysis.
Part V, "Global Patterns and Processes," is one of the best. Beginning with a superb unit on basic global climate that should be read just for fun, the transition to biome physiognomy in the last sections and the following chapter (Chapter 19) is smooth. Chapter 20 on regional and global diversity is a unique and brilliant follow-up to the biome chapters, the ideas are stimulating, and the way that both old and new material are integrated ought to change some syllabi. Although none of the review team can claim paleological expertise, this short but nicely placed chapter is almost as good a read as the unit on global climate. Our one recommendation is that this chapter could be better connected with the section on communities.
Global change issues such as global warming, nitrogen deposition, invasive species, and habitat fragmentation are presented in well-organized detail in the concluding chapter of The Ecology of Plants. These topics are increasingly an important component of ecology that have traditionally been given short shrift in texts. Global warming is clearly tied to Chapter 2 on carbon uptake and Chapter 15 on the carbon cycle and productivity. Increasing atmospheric CO2 is explained, and these effects on plants are separated clearly from the cascading effects of CO2 on temperature and the effects of temperature on plants. The fluxes in the carbon cycle figure correspond reasonably well with those in Houghton et al. (1995
); however, the section would be improved by a simple layman's explanation of how greenhouse molecules comprising a tiny fraction of the atmosphere can force global warming. We were told to go to Chapter 2 for comments on the effects of CO2 on temperature, but this didn't help much. We would have loved to have seen the Croll-Milancovi
theory for long-term climate change integrated with their presentation of the greenhouse-gas forcing theory for global warming. To one of us, Chapter 22 did not express reasonable (read "any") skepticism for the predictive global change scenarios presented and took on a decidedly biased political tone when discussing fossil fuel combustion. However, these opinions should not be taken as reasons to dismiss a very good final chapter in an excellent Part V.
Our complaints about the organization of The Ecology of Plants should not be taken as a dismissal of the book as a high-quality text. On the contrary, even with its organizational shortcomings, this book provides the most comprehensive, well-integrated, and accessible treatment of plant ecology available and is perfectly suited for undergraduate teaching. Gurevitch et al. use pictures, graphs, and diagrams liberally. They use box insets frequently and effectively. A wonderful aspect of the book is the sprinkling of names and pictures of many ecologists that are cited in the text. All of these features make for an engaging text that should provide stimulating reading for undergraduates and a useful reference for more advanced students.
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FOOTNOTES |
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LITERATURE CITED |
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 TOP LITERATURE CITED |
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Cain M. L. 1994 Consequences of foraging in clonal plant species. Ecology 75: 933-944[CrossRef][ISI]
Callaway R. M. 1995 Positive interactions among plants. Botanical Review 61: 306-349
Callaway R. M. E. T. Aschehoug 2000 Invasive plants versus their new and old neighbors: a mechanism for exotic invasion. Science 290: 521-523
de Kroon H. J. van Groenendael 1997 The ecology and evolution of clonal growth in plants. Backhuys Publishers, Leiden, Netherlands
Harper J. L. 1961 Approaches to the study of plant competition. Symposium for the Society of Experimental Biology 15: 1-39
Houghton J. T. L. G. Meira Filho B. A. Callander N. Harris A. Kattenberg K. Maskell 1995 Climate change 1995. Cambridge University Press, Cambridge, UK
Hubbell S. P. 2001 The unified neutral theory of biodiversity and biogeography. Monographs in population biology. Princeton University, Princeton, New Jersey, USA
Levine J. M. 1999 Indirect facilitation: evidence and predictions from a riparian community. Ecology 80: 1762-1769[CrossRef][ISI]
Mack R. N. D. Simberloff W. M. Lonsdale H. Evans M. Clout F. A. Bazzaz 2000 Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications 10: 689-710[CrossRef][ISI]
McNaughton S. J. 1983 Serengeti grassland ecology: the role of composite environmental factors and contingency in community organization. Ecological Monographs 53: 291-320[CrossRef]
Miller T. E. 1994 Direct and indirect species interactions in an early old-field community. American Naturalist 143: 1007-1025[CrossRef][ISI]
Power M. E. D. Tilman J. A. Estes B. A. Menge W. J. Bond L. S. Mills D. Gretchen J. C. Castilla J. Lubchenco R. T. Paine 1996 Challenges in the quest for keystones. BioScience 46: 609-620[CrossRef][ISI]
Root R. B. 1996 Herbivore pressure on goldenrods (Solidago altissima): its variation and cumulative effects. Ecology 77: 1074-1087[CrossRef][ISI]
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