The Functional Consequences of Biodiversity: Empirical Progress and Theoretical Extensions (MPB-33)

by Ann P. Kinzig, Stephen Pacala, David Tilman

Overview

Does biodiversity influence how ecosystems function? Might diversity loss affect the ability of ecosystems to deliver services of benefit to humankind? Ecosystems provide food, fuel, fiber, and drinkable water, regulate local and regional climate, and recycle needed nutrients, among other things. An ecosyste's ability to sustain functioning may depend on the number of species residing in the ecosystem—its biological diversity—but this has been a controversial hypothesis. There are many unanswered questions about how and why changes in biodiversity could alter ecosystem functioning. This volume, written by top researchers, synthesizes empirical studies on the relationship between biodiversity and ecosystem functioning and extends that knowledge using a novel and coordinated set of models and theoretical approaches.


These experimental and theoretical analyses demonstrate that functioning usually increases with biodiversity, but also reveals when and under what circumstances other relationships between biodiversity and ecosystem functioning might occur. It also accounts for apparent changes in diversity-functioning relationships that emerge over time in disturbed ecosystems, thereby addressing a major controversy in the field. The volume concludes with a blueprint for moving beyond small-scale studies to regional ones—a move of enormous significance for policy and conservation but one that will entail tackling some of the most fundamental challenges in ecology.


In addition to the editors, the contributors are Juan Armesto, Claudia Neuhauser, Andy Hector, Clarence Lehman, Peter Kareiva, Sharon Lawler, Peter Chesson, Teri Balser, Mary K. Firestone, Robert Holt, Michel Loreau, Johannes Knops, David Wedin, Peter Reich, Shahid Naeem, Bernhard Schmid, Jasmin Joshi, and Felix Schläpfer.

Product Details

ISBN-13:	9780691088228
Publisher:	Princeton University Press
Publication date:	02/17/2002
Series:	Monographs in Population Biology , #33
Pages:	392
Product dimensions:	5.50(w) x 8.50(h) x (d)

About the Author

Ann P. Kinzig is Assistant Professor of Biology at Arizona State University. Stephen Pacala is Frederick D. Petrie Professor of Ecology and Evolutionary Biology at Princeton University. G. David Tilman is Distinguished McKnight University Professor of Biology at the University of Minnesota and the author or editor of several books, including Spatial Ecology (Princeton).

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CHAPTER ONE

Opening Remarks

Ann P. Kinzig

Darwin first proposed a connection between biodiversity and ecosystem functioning in 1859. Interest in the topic has mainly waned—sometimes waxed—in the time interval since. In the last few decades, however, the waxing has had the upper hand, and a quick trip through an electronic archive reveals over 100 articles on this topic since 1982.

Why then a book on the subject? First, there have been significant advances in our empirical understanding of the diversity-functioning relationship in the last few years, but those results have not been compiled, evaluated, and synthesized in both a comprehensive and detailed manner elsewhere. Second, we offer new theoretical results that advance our understanding of when and under what circumstances certain forms of the diversity-functioning relationship might emerge. Third, while knowledge of consumer and decomposer influences on diversity-functioning relationships has not advanced in the last decade as much as many of us had hoped it would, some sensible recommendations for focusing research efforts can be made, andwe offer those here. Perhaps most importantly, our analysis of the existing experimental record yielded some surprising results, and our attempts to explain those results and extend them with development of new theory significantly influenced our perceptions of the mechanisms governing diversity and ecosystem functioning relationships.

This book, then, is organized into three parts—a synthesis of the existing experimental and theoretical work and the interpretation of each in light of the other, new contributions to theory that extend the experimental results, and a discussion of future directions.

The first section leads with a chapter by Tilman and Lehman that presents the current prevailing theories of the mechanisms governing the diversity-functioning relationship, and the evidence for or against these mechanisms in early experimental results. The next two chapters—by Tilman et al. (chapter 3) and Hector (chapter 4)—give detailed analyses of the two most extensive diversity-functioning experiments to date, in the grasslands of Minnesota and Europe, respectively. Naeem (chapter 5) reviews the literature on trophic interactions and microbial influences on ecosystem processes, and offers suggestions for advancing the field using both theoretical and empirical approaches. In chapter 6, Schmid, Joshi, and Schläpfer offer a comprehensive review of experimental and observational studies that should serve as one of the most useful compilations of approaches and results for any serious scholar in this field. Pacala and Tilman (chapter 7) conclude this section with a discussion of the biggest surprises that have emerged in the existing experimental record, and provide some simple explanations for these surprises.

In spite of the advances made in the experimental record, however, practical limitations simply preclude experiments that can span the large spatial scales, the long temporal scales, and the representative diversity gradients and structures that are properly the concern of work in this area. Thus we use the next section, on theory, to extend diversity-functioning results to scales that are not particularly amenable to experimental manipulations—landscape-level (as opposed to plot-level) processes, the long time dynamics that govern and characterize natural systems, and multitrophic-level interactions. In doing so, we take a very specific approach. In particular, we employ a common ecosystem model and "attach" to that common model different models of species coexistence. We can thus attribute differences in outcome to differences in coexistence mechanisms, rather than to differences in approaches taken for simulating decomposition, mineralization, and so forth. The common model is general enough to accommodate many of the ecosystem processes of interest, and is presented in chapter 8. Kinzig and Pacala (chapter 9) then look at "successional niche" models—processes of succession in lightly disturbed environments or competition-colonization dynamics in more heavily disturbed environments. Chesson, Pacala, and Neuhauser (chapter 10) examine diversity-functioning relationships when coexistence is maintained by spatial or temporal heterogeneity—a patchwork of soil types, or changing climatic conditions throughout seasons, for instance. Finally, Holt and Loreau (chapter 11) examine simple models of trophic interactions and contrast their results with the previous chapters, where only the plant community was explicitly included in the ecosystem model.

In the last section of the book Balser, Kinzig, and Firestone (chapter 12) sift the literature on the influences of microbial diversity on ecosystem functioning, and offer a framework for guiding future work in this area. Lawler, Armesto, and Kareiva (chapter 13) examine the implications of these scientific findings for conservation. Finally, in the last chapter, the editors offer a synthesis of the major conclusions, and a blueprint for future research directions.

This book is not, however, the last word on the subject of diversity-functioning relationships. In fact, the characterization of any vigorous scientific field is that obsolescence begins the moment a project is conceived. So too with our efforts. In particular, when we developed the approach used in the theory section, well over three years ago now, the early experimental results all seemed consistent with a sampling mechanism—that is, dominance of polycultures by a single best competitor, and a best polyculture performance that equaled, but did not exceed, the best monoculture performance.

We now see experimental results that differ from these—a "transition," if you will, between a sampling mechanism to niche-partitioning or niche-complementarity mechanisms. These niche mechanisms permit an "overyielding" effect—where the best polyculture can outperform the best monoculture. This observed transition justifies some of the early criticisms of Huston (1997), Aarssen (1997), and others—namely, that what we were seeing in the initial experimental results was domination by the "weediest," fastest-growing species, a dynamic that has little to do with any interesting features of diversity-functioning relationships. These experimental outcomes also force us to revisit the earlier analyses of MacArthur, where just such niche complementarity and overyielding were predicted to occur.

Nonetheless, the early experimental results, and the overly harsh discreditation of MacArthur's work, led us to focus on possible sampling mechanisms over niche-complementarity mechanisms. Thus, while we include some complementarity mechanisms in the theory section (see, particularly, chapter 10), we overlook other classes of models that might have proved useful in interpreting observed relationships and extending experimental results. We return to this point in the concluding chapter.

In retrospect, we should not have been surprised by this transition from sampling to niche complementarity. As ecologists, we know that systems away from equilibrium (as planted plots in experimental manipulations certainly are) can be characterized by two (or more) distinctive time dynamics—an initial, rapid response that has to do with early growth dynamics, and a longer-term response governed by competitive interactions and population dynamics. (Pacala and Tilman elaborate on these points, and offer formal mathematical representations, in chapter 7.) Thus, we should have expected potentially significant changes in outcomes as time wore on. Nor should we have been surprised by the emergence of niche complementarity—we know that species coexist, and we understand that this coexistence can mean changes in performance that do not "balance out" between monocultures and polycultures.

In addition, the analyses presented in this book illuminate some conspicuous exceptions to the generally expected result that ecosystem functioning will increase with diversity, and that the performance of the best polycultures will equal or exceed the performances of the best, but more depauperate, communities. In particular, there is some experimental evidence for declining functioning with increasing diversity, and this same pattern emerges from the theories developed for communities where coexistence is maintained by successional niches or interference competition. These outcomes can be understood by considering the relationship between competitive ability and the performance of certain ecosystem processes. Ultimately, the influence of diversity per se on ecosystem functioning should depend on those mechanisms permitting coexistence in particular systems, and on how those strategies that permit competitive superiority or dominance in these coexistence battles influence performance at both local and landscape scales. For instance, are competitive rank and performance of certain functions "parallel," with the superior competitor being the superior performer? Or are they "orthogonal," with no discernible relationship between competitive ability and performance? Might a superior competitor have high local performance but low landscape performance due to low abundance and suppression of other types? How do these relationships between competition and performance depend on scale, or on the coexistence mechanism operating, or on the ecosystem process being examined?

These emerging insights into the more complicated dynamics and mechanisms governing diversity-functioning relationships provide one of the most compelling reasons for further study in this area—namely, that disentangling the influences of diversity on ecosystem functioning, across space and time, requires that we deepen our understanding of the answers to some of the most compelling questions in ecology. How do species coexist? Why do we see so many together, and why don't we see more? How do insights into patterns and processes derived at one spatial and temporal scale translate across other scales? How do communities assemble, how do they disassemble, and how do these rules change when humans decide to rearrange their surroundings? (See Levin 1999 for a wonderful exposition on many of these questions.) Ultimately, then, the study of biodiversity-ecosystem functioning relationships is no more and no less than the study of some of the most fundamental questions in ecology.

Finally, though, we are citizens as well as scientists, with an interest in sustaining critical ecosystem processes and species integrity, which are under increasing assault from the sheer magnitude of the human endeavor. We therefore cannot ignore the social, ethical, and political implications of our work in this field—what it might mean for the design and control of managed systems, for the likely responses of ecosystems to global change and the policies needed to mediate those responses, for the choices we must make in the species triage we conduct every day. We only touch on some of those implications in this volume, but as scientists and as citizens we are acutely aware of them. We do hope, after all, to leave a world that sustains human well-being, and to leave a world in which tomorrow's scientists can answer the questions we fail to answer today.

Table of Contents

	Preface	xiii
	List of Contributors	xix
	List of Figures	xxi
	List of Tables	xxv
1.	Opening Remarks	1
Part 1	Empirical Progress
2.	Biodiversity, Composition, and Ecosystem Processes: Theory and Concepts	9
	Introduction	9
	Definitions of Diversity	11
	Diversity, Productivity, and Resource Dynamics	15
	Diversity and Stability	29
	Summary	39
	Acknowledgments	41
3.	Experimental and Observational Studies of Diversity, Productivity, and Stability	42
	Diversity and Stability	43
	Diversity, Productivity, and Nutrient Dynamics	49
	New Results from the Cedar Creek Biodiversity Experiment	53
	Summary and Synthesis	67
	Acknowledgments	70
4.	Biodiversity and the Functioning of Grassland Ecosystems: Multi-Site Comparisons	71
	Introduction	71
	The Biodepth Project	72
	Summary of the Biodepth Results	89
	Comparisons with Related Studies	89
	Summary	94
	Acknowledgments	95
5.	Autotrophic-Heterotrophic Interactions and Their Impacts on Biodiversity and Ecosystem Functioning	96
	Introduction	96
	Fundamentals	98
	Fundamental Trophic Structure	101
	Heterotrophic Diversity and Ecosystem Functioning	101
	Implications for Autotroph-Only Models	112
	Discussion	114
6.	Empirical Evidence for Biodiversity-Ecosystem Functioning Relationships	120
	Introduction	120
	Plant Diversity Effects on Ecosystem Functioning	123
	Biodiversity Effects among Trophic Levels	140
	Designing Empirical Studies to Measure Biodiversity-Ecosystem Functioning Relationships	141
	Acknowledgments	150
7.	The Transition from Sampling to Complementarity	151
	Conclusions	165
Part 2	Theoretical Extensions
8.	Introduction to Theory and the Common Ecosystem Model	169
	The Common Ecosystem Model	171
	Summary of the Basic Model	174
9.	Successional Biodiversity and Ecosystem Functioning	175
	Introduction	175
	The Successional Niche in a Simple Mechanistic Ecosystem Model	179
	Competition-Colonization in a Simple Mechanistic Ecosystem Model	193
	Conclusions	212
10.	Environmental Niches and Ecosystem Functioning	213
	Introduction	213
	Environmental Niches	215
	Ecosystem Functioning	223
	Discussion	237
	Acknowledgments	244
	Appendix	245
11.	Biodiversity and Ecosystem Functioning: The Role of Trophic Interactions and the Importance of System Openness	246
	Introduction	246
	The Sampling Effect Model and Community Assembly	247
	Importance of Trophic Complexity and System Openness	248
	Toward an Ecosystem Model with Trophic Interactions	250
	Discussion	256
	Conclusions	259
	Acknowledgments	262
Part 3	Applications and Future Directions
12.	Linking Soil Microbial Communities and Ecosystem Functioning	265
	Introduction	265
	Challenges in Linking Microbial Communities and Ecosystem Functioning	266
	Linking Microbial Community Composition and Ecosystem Functioning: A Review of Concepts and Models	271
	Timeline of Microbial Response: Conceptual Model of Microbial Role in Ecosystem Functioning	278
	Conclusions and Future Research Needs	285
	Acknowledgments	287
	Appendix	287
13.	How Relevant to Conservation Are Studies Linking Biodiversity and Ecosystem Functioning?	294
	Introduction	294
	Conservation Philosophies and Ecological Science	295
	Studies of Biodiversity-Ecosystem Functioning Relationships: Origins and Recent Critiques	298
	Four Unresolved Issues	301
	Relating Biodiversity Theory and Experiments to Losses in Biodiversity Caused by Humans	308
	Acknowledgments	313
14.	Looking Back and Peering Forward	314
	References	331
	Index	359

What People are Saying About This

Lawton

An exciting, timely, and unique book by a powerful team of authors. No other text competes with it. It will be the standard reference on the relationship between biodiversity and ecosystem functioning for the next five, even ten years.
— John H. Lawton, Chief Executive, Natural Environment Research Council, United Kingdom

From the Publisher

"An exciting, timely, and unique book by a powerful team of authors. No other text competes with it. It will be the standard reference on the relationship between biodiversity and ecosystem functioning for the next five, even ten years."—John H. Lawton, Chief Executive, Natural Environment Research Council, United Kingdom

"This book, written by superb authors, fills a major need in that it unites a discussion of pioneering research on the role of biodiversity in ecosystem function and relates these experiments to a common theoretical framework. The idea of bringing to bear a standardized and commonly accepted ecosystem function model on the biodiversity question is ingenious and of great value."—Peter Kareiva, Lead Scientist, The Nature Conservancy

"This exceptionally well-edited book summarizes, successfully, our current knowledge on the ecosystem functioning of biodiversity. It does much more, however: through the clever use of a standard model to explore various aspects of the issue, it greatly extends our understanding. The authors, who are all at the top of their fields, provide a wonderfully creative and useful analysis that goes a long way to explaining the true nature of the controversy that has plagued the field in the past couple of years. The Functional Consequences of Biodiversity provides a well-marked path for future work."—Harold Mooney, Stanford University

Harold Mooney

This exceptionally well-edited book summarizes, successfully, our current knowledge on the ecosystem functioning of biodiversity. It does much more, however: through the clever use of a standard model to explore various aspects of the issue, it greatly extends our understanding. The authors, who are all at the top of their fields, provide a wonderfully creative and useful analysis that goes a long way to explaining the true nature of the controversy that has plagued the field in the past couple of years. The Functional Consequences of Biodiversity provides a well-marked path for future work.
— Harold Mooney, Stanford University

Peter Kareiva

This book, written by superb authors, fills a major need in that it unites a discussion of pioneering research on the role of biodiversity in ecosystem function and relates these experiments to a common theoretical framework. The idea of bringing to bear a standardized and commonly accepted ecosystem function model on the biodiversity question is ingenious and of great value.
— Peter Kareiva, Lead Scientist, The Nature Conservancy

Editorial Reviews

"An exciting, timely, and unique book by a powerful team of authors. No other text competes with it. It will be the standard reference on the relationship between biodiversity and ecosystem functioning for the next five, even ten years."—John H. Lawton, Chief Executive, Natural Environment Research Council, United Kingdom


"This book, written by superb authors, fills a major need in that it unites a discussion of pioneering research on the role of biodiversity in ecosystem function and relates these experiments to a common theoretical framework. The idea of bringing to bear a standardized and commonly accepted ecosystem function model on the biodiversity question is ingenious and of great value."—Peter Kareiva, Lead Scientist, The Nature Conservancy


"This exceptionally well-edited book summarizes, successfully, our current knowledge on the ecosystem functioning of biodiversity. It does much more, however: through the clever use of a standard model to explore various aspects of the issue, it greatly extends our understanding. The authors, who are all at the top of their fields, provide a wonderfully creative and useful analysis that goes a long way to explaining the true nature of the controversy that has plagued the field in the past couple of years. The Functional Consequences of Biodiversity provides a well-marked path for future work."—Harold Mooney, Stanford University

From the Publisher