Introduction. Methods in Ecosystem
Science: Progress, Tradeoffs,
and Limitations
Osvaldo E. Sala, Robert B. Jackson, Harold A. Mooney, and Robert W. Howarth
Ecosystem science is a relatively young field of
ecology dealing with all of the organisms in an area
and their relationships with the physical environment (Odum 1959). It includes plants, animals, and
microorganisms, and studies the interactions
among them and with the soil, water, and the atmosphere. In pursuing general patterns at the ecosystem level, and when trying to understand the
mechanisms controlling these patterns, ecosystem
scientists study the flow of energy and the cycling
of material, including water and elements, such as
carbon, nitrogen, and phosphorus. The rapid
growth in ecosystem science during the last 20
years partially resulted from its unique relationship
to other disciplines. Ecosystem science has articulated the role of organisms with the physical environment and emphasized the feedback of human
activities with the atmosphere, rivers, and open
oceans. The demands of global change research and
earth-system studies are only likely to increase the
importance of ecosystem studies in the future.
As ecosystem science grew and gained its identity, scientists began to develop their own methods
for studying ecosystem processes. Some of these
methods were developed ex novo, while some others were adapted from such disciplines as chemistry, physics, and physiology. The development of
new tools fostered new concepts in ecosystem science, while new theories led to the development of
new techniques in a synergistic interaction between
theory and methods. For example, continuous flow
mass spectrometers opened the possibility of using
stable isotopes as a tool for studying water and nutrient dynamics in ecosystems. These new capabilities, in tum, stimulated a wealth of model and theoretical developments on isotopic discrimination by
different ecosystem processes (see Chapters 8 and
12). The progress of ecosystem science is limited
simultaneously by both theory and methods, as has
been demonstrated by the benefits of introducing
simulation models and remote sensing tools into
ecological research (see Chapters 3 and 25). This
book suggests that there are methods limitations,
such as real-time root observation techniques, automated tissue grinders, or chamberless methods
for flux measurements. These represent just some
examples of methodological constraints, but they
are not necessarily the only or the most important
limitations.
The objectives of this book are to review the
methods most commonly used in ecosystem science and to assess their advantages and disadvantages. Each chapter reviews the basic ecological concepts behind each method, describes the
methods most commonly used and those increasing
in importance, and examines tradeoffs among alternatives. The aim of the book is to help scholars
explore new areas and make decisions about the
best methods to answer particular ecosystem questions. Because of the breadth of ecosystem science,
the book cannot possibly describe all methods in
detail, but instead provides information for choosing among methods and guidance for locating detailed information about particular techniques.
When good reviews of particular techniques exist,
some authors have chosen to direct the reader to
those reviews, and concentrate on other methods
less well described.
The range of methods in ecosystem science is
one of our discipline's strengths, but it also poses
Science: Progress, Tradeoffs,
and Limitations
Osvaldo E. Sala, Robert B. Jackson, Harold A. Mooney, and Robert W. Howarth
Ecosystem science is a relatively young field of
ecology dealing with all of the organisms in an area
and their relationships with the physical environment (Odum 1959). It includes plants, animals, and
microorganisms, and studies the interactions
among them and with the soil, water, and the atmosphere. In pursuing general patterns at the ecosystem level, and when trying to understand the
mechanisms controlling these patterns, ecosystem
scientists study the flow of energy and the cycling
of material, including water and elements, such as
carbon, nitrogen, and phosphorus. The rapid
growth in ecosystem science during the last 20
years partially resulted from its unique relationship
to other disciplines. Ecosystem science has articulated the role of organisms with the physical environment and emphasized the feedback of human
activities with the atmosphere, rivers, and open
oceans. The demands of global change research and
earth-system studies are only likely to increase the
importance of ecosystem studies in the future.
As ecosystem science grew and gained its identity, scientists began to develop their own methods
for studying ecosystem processes. Some of these
methods were developed ex novo, while some others were adapted from such disciplines as chemistry, physics, and physiology. The development of
new tools fostered new concepts in ecosystem science, while new theories led to the development of
new techniques in a synergistic interaction between
theory and methods. For example, continuous flow
mass spectrometers opened the possibility of using
stable isotopes as a tool for studying water and nutrient dynamics in ecosystems. These new capabilities, in tum, stimulated a wealth of model and theoretical developments on isotopic discrimination by
different ecosystem processes (see Chapters 8 and
12). The progress of ecosystem science is limited
simultaneously by both theory and methods, as has
been demonstrated by the benefits of introducing
simulation models and remote sensing tools into
ecological research (see Chapters 3 and 25). This
book suggests that there are methods limitations,
such as real-time root observation techniques, automated tissue grinders, or chamberless methods
for flux measurements. These represent just some
examples of methodological constraints, but they
are not necessarily the only or the most important
limitations.
The objectives of this book are to review the
methods most commonly used in ecosystem science and to assess their advantages and disadvantages. Each chapter reviews the basic ecological concepts behind each method, describes the
methods most commonly used and those increasing
in importance, and examines tradeoffs among alternatives. The aim of the book is to help scholars
explore new areas and make decisions about the
best methods to answer particular ecosystem questions. Because of the breadth of ecosystem science,
the book cannot possibly describe all methods in
detail, but instead provides information for choosing among methods and guidance for locating detailed information about particular techniques.
When good reviews of particular techniques exist,
some authors have chosen to direct the reader to
those reviews, and concentrate on other methods
less well described.
The range of methods in ecosystem science is
one of our discipline's strengths, but it also poses