Table Of ContentPattern and Process in a
Forested Ecosystem
F. Herbert Bormann
Gene E. Likens
Pattern and Process I• n a
Forested Ecosystem
Disturbance, Development and the Steady State
Based on the Hubbard Brook Ecosystem Study
Springer-Verlag
New York Berlin Heidelberg London
Paris Tokyo Hong Kong Barcelona
F. Herbert Bormann
School of Forestry and Environmental Studies
Yale University
New Haven, Connecticut 06511, USA
Gene E. Likens
Institute of Ecosystem Studies
Millbrook, New York 12545, USA
Library of Congress Cataloging in Publication Data
Bormann, F. Herbert, 1922-
Pattern and process in a forested ecosystem.
Bibliography: p.
Includes index.
1. Forest ecology-New Hampshire-Hubbard Brook
Valley. 1. Likens, Gene E., 1935- joint author.
II. Title.
QH105.N4B67 574.5'264
ISBN-\3: 978-0-387-94344-2 e-ISBN-13: 978-1-4612-6232-9
001: 10.1007/978-1-4612-6232-9
© 1994 Springer-Verlag New York, Inc.
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9 8 7 6 5 4 3 2 1
Preface
The advent of ecosystem ecology has created great difficulties for
ecologists primarily trained as biologists, since inevitably as the field grew,
it absorbed components of other disciplines relatively foreign to most
ecologists yet vital to the understanding of the structure and function of
ecosystems. From the point of view of the biological ecologist struggling
to understand the enormous complexity of the biological functions within
an ecosystem, the added necessity of integrating biology with geochemis
try, hydrology, micrometeorology, geomorphology, pedology, and applied
sciences (like silviculture and land use management) often has appeared
as an impossible requirement. Ecologists have frequently responded by
limiting their perspective to biology with the result that the modeling of
species interactions is sometimes considered as modeling ecosystems, or
modeling the living fraction of the ecosystems is considered as modeling
whole ecosystems. Such of course is not the case, since understanding the
structure and function of ecosystems requires sound understanding of
inanimate as well as animate processes and often neither can be under
stood without the other.
About 15 years ago, a view of ecology somewhat different from most
then prevailing, coupled with a strong dose of naivete and a sense of
exploration, lead us to believe that consideration of the inanimate side of
ecosystem function rather than being just one more annoying complexity
might provide exceptional advantages in the study of ecosystems. To
examine this possibility, we took two steps which occurred more or less
simultaneously. We developed an ecosystem model that-heavily involves
inanimate as well as animate processes, and we devised a way of
vi Preface
calculating some of the major parameters of that model that hitherto
could be estimated only with great difficulty.
Our model, which will be described more fully in the subsequent text,
conceives of the terrestrial ecosystem as a delimited part of the biogeo
chemical cycles of the earth. The ecosystem is an open system; it receives
energy from the sun and materials and energy from the biogeochemical
cycles. It processes these materials and discharges outputs to the larger
cycles. Activities within the ecosystem are largely governed by the nature
of inputs, and man can have major effects on the structure and function of
ecosystems by advertent or inadvertent effects on inputs. Similarly, man
can have major effects on the nature of outputs from ecosystems by the
kinds of manipUlations he consciously or inadvertently promotes within
ecosystems. These outputs enter the larger biogeochemical cycles and
have the potential of affecting interconnected ecosystems; in other words,
one system's outputs become another's inputs. In this light, inputs and
outputs can be seen as linkages transmitting the effects of natural or
man-made activities between ecosystems. Not only does our concept of the
ecosystem emphasize relationships between systems, but it provides a
frame whereby the ecosystem can grow or decline in response to
natural or man-made developments imposed upon it. Phenomena such as
weathering, nitrogen fixation, or biomass accumulation can be evalu
ated in an ecosystem context, and species strategies can be studied in
relation to temporal and spatial biogeochemical variations.
Our ecosystem model probably would have remained an intellectual
curiosity had we not conceived of the "small watershed technique" for
measuring input-output relationships. This technique considers a small
watertight watershed as the delimited ecosystem. As explained in the text,
this permits a fairly precise measurement of both input and output of
certain nutrients and it permits the construction of partial nutrient
budgets. These budgets, coupled with the measurement of parameters
within the ecosystem such as productivity, biomass accumulation, canopy
leaching, litter fall, and so forth allow the quantification of more complete
nutrient budgets. By budget balancing, often we are able to estimate
processes that are otherwise very difficult to estimate such as rock
weathering, nitrogen fixation, or sulfur impaction.
Not only does the small watershed technique allow quantification of the
structure and functions of natural ecosystems, but once having established
base-line biogeochemistry, it is possible to develop a program in
experimental ecosystem ecology wherein treatments are imposed on
entire watershed-ecosystems and responses of the treated system are
compared to undisturbed systems. This approach not only yields consid
erable information on the effects of the treatments but also allows
quantification of some processes occurring in the undisturbed system that
are otherwise unmeasureable.
In our first volume, Biogeochemistry of a Forested Ecosystem, we
presented a detailed examination of the biogeochemistry of an aggrading
Preface vii
northern hardwood watershed-ecosystem. The primary consideration was
on the physical aspects of hydrologic and nutrient flow through the
ecosystem and on hydrologic and nutrient budgets.
This volume has as its major concern the presentation of an integrated
view of the structure, functions, and development of the northern
hardwood ecosystem. It concentrates on the interrelationships among
biogeochemical processes, animate and inanimate structure of the ecosys
tem, species behavior within the ecosystem, and how these relationships
change through time following a perturbation. For biogeochemical infor
mation it draws heavily on our first volume, but emphasis is placed on the
role of biological processes in controlling destabilizing forces to which
every ecosystem is continually subjected.
Not only was it our goal to present an integrated view of ecosystem
development, but we thought the text should serve, as well, as a teaching
tool for natural scientists interested in the structure and function of
ecosystems. To that end, we have made a special attempt to detail the
reasoning used to reach pivotal conclusions, to separate conclusions based
largely on fact from those based largely on speculation and, in general, to
write for the reader interested in the ecology of ecosystems rather than
for the ecosystem specialist. This is not to deny that concentrated effort
on the part of the reader will be required. After all, the ecology of
ecosystems is among the most complex of subjects and inevitably some of
that complexity must be reflected in the text.
Acknowledgments
Any scientist working to develop new knowledge owes an incredible debt
to those who came before. We wish to acknowledge four persons whose
divergent influences converged in a kind of spontaneous generation to
give rise to the Hubbard Brook Ecosystem Study. Eugene P. Odum set
the scene with his articulate and enthusiastic advocacy for the ecosystem
as a basic unit of study in ecology. Murray F. Buell and Henry J. Oosting
with their research and teaching emphasis on succession and climax
provided the time frame for the developmental aspects of our study, while
Arthur D. Hasler's success with experimental manipulation of lake
ecosystems lead us to believe that similar success with our systems would
be possible. To this group, we add W. Dwight Billings whose encourage
ment and gentle hectoring led to the writing of this volume.
The Hubbard Brook Ecosystem Study is the product of the minds,
hands, and enthusiasm of scores of people. In our first volume, we
acknowledged 151 persons whose contributions, great and small, made
that volume and the present volume possible. To that list we now add: A.
Bormann, H. Buell, T. Butler, J. Cole, P. Coleman, P. Doering, E.
Edgerton, J. Ford, C. Goulden, M. Hall, R. Hall, W. Hanson, R. Harkov, T.
Hayes, G. Hendrey, D. Hill, W. McDowell, R. Moore, S. Nodvin, J.
Sherman, J. Sloane, and J. Teffer. We are also indebted to L. Auchmoody, J.
viii Preface
Baker, R. Campbell, V. Jensen, V. Johnson, E. Kelso, and R. McDonald of
the U.S. Forest Service, and especially to J. Miller of the Yale Library for
ideas and information on fire and other subjects. For major contributions
to the preparation of the manuscript and editorial assistance, we thank
Chris Bormann and Rebecca Bormann. Phyllis Toyryla not only typed the
manuscript, but provided vital and enthusiastic assistance throughol,lt the
preparation of the manuscript.
For keeping us within modest bounds of scientific rigor, we are
indebted to colleagues who generously gave their time to read portions of
our manuscript. As a result of insightful criticism, perceptive editing, and
timely ideas we think the manuscript improved. We also have been made
aware that a few of our cherished conclusions are viewed by some as
thickets of muddled thinking. We thank all of the following for trying to
keep us on a straight and narrow path: S. Bicknell, J. Eaton, R. Holmes,
J. Hornbeck, S. Levin (in vino veritas), J. Melillo, D. Ryan, T. Siccama, L.
Tritton, and T. Wood. Special thanks are due J. Aber, W. Covington, A.
Federer, C. Hall, O. Loucks, P. Marks, W. Martin, W. Niering, S. Pilgrim, K.
Reed, G. Whitney, and R. Whittaker who reviewed major sections of the
book and made dozens of thoughtful suggestions.
We also acknowledge our debt to the National Science Foundation
which has supported our work during the last 15 years and to the U.S.
Forest Service for making it possible for us to use the Hubbard Brook
Experimental Forest as well as to share in the ideas and data accumulated
by scientists of the U.S. Forest Service at Hubbard Brook. We add,
however, that the ideas expressed here are not necessarily those of the
U.S. Forest Service. Finally, space is too short to adequately recognize
the overall contributions of Robert S. Pierce. Not only has he been our
colleague in the design and execution of science, but major credit for
the success of the Hubbard Brook Ecosystem Study is due to his unob
trusive but extraordinary capacity to coordinate and manage a complex
enterprise.
Contents
Chapter 1
The Northern Hardwood Forest: A Model for Ecosystem
Development 1
Objectives 1
Limits for Our Theoretical Model of Ecosystem Development 6
Biomass Accumulation After Clear-Cutting 12
The Hubbard Brook Ecosystem Study 27
Summary 39
Chapter 2
Energetics, Biomass, Hydrology, and Biogeochemistry of
the Aggrading Ecosystem 41
Solar Energy Flow 43
Biomass: Development of Regulation and Inertia 48
Detrital-Grazing Cycles 50
Biotic Regulation of Biogeochemical Flux 55
Nutrient Reservoirs Within the Aggrading Ecosystem 70
Sources of Nutrients for the Aggrading Ecosystem 72
Circulation and Retention of Nutrients 73
Summary 78
x Contents
Chapter 3
Reorganization: Loss of Biotic Regulation 81
A Deforestation Experiment 82
Relationship of the Deforestation Experiment to Commercial
Clear-Cutting 100
Summary 101
Chapter 4
Development of Vegetation After Clear-Cutting: Species
Strategies and Plant Community Dynamics 103
What is Secondary Succession? 103
Reproductive and Growth Strategies Responsive to Perturba-
tions That Open the Forest Canopy 104
The Buried-Seed Strategy 108
Floristic Response to Removal of the Forest Canopy by
Clear-Cutting 113
Differentiation of the Vegetation Established Immediately After
Clear-Cutting 115
Growth Strategies Underlying Initial Canopy Differentiation 118
Morphogenesis and Growth Strategy 125
Endogenous Disturbance 129
Interactions Between Reproductive Strategies and Degree of
Canopy Disturbance 131
Composition of the Dominant Layer During Ecosystem Develop-
ment After Clear-Cutting 133
Species Richness 135
Summary 136
Chapter 5
Reorganization: Recovery of Biotic Regulation 138
Primary Productivity 139
Recovery of Biotic Regulation Over Ecosystem Export 143
Coupling of Mineralization and Storage Processes 153
Replacement of Lost Nutrient Capital 157
Ecosystem Regulation 157
Summary 163
Chapter 6
Ecosystem Development and the Steady State 164
Evidence for a Steady State 165
Steady-State Models 166
Living Biomass Accumulation 167
Contents xi
Total Biomass Accumulation 168
The Plot as a Unit of Study 168
Trends Associated With Ecosystem Development 177
Summary 191
Chapter 7
The Steady State as a Component of the Landscape 192
Exogenous Disturbance Defined 194
Comparative Effects of Major Perturbations 195
Disturbance in Presettlement Northern Hardwood Forests 197
Postsettlement Disturbance 207
Increased Regularity of Whole-System Biomass Oscillation 210
Summary 211
Chapter 8
Forest Harvest and Landscape Management 213
Air Pollution 213
Forest Harvesting Practices 216
Landscape Management 227
References 229
Index 245
Description:The advent of ecosystem ecology has created great difficulties for ecologists primarily trained as biologists, since inevitably as the field grew, it absorbed components of other disciplines relatively foreign to most ecologists yet vital to the understanding of the structure and function of ecosyst
