Ecology of Soil Seed Banks

457 Pages·1989·7.379 MB·English

by  Mary Allessio Leck (Eds.)

Ecology of
Soil Seed Banks
Edited by
Mary Allessio Leek
Department of Biology
Rider College
Lawrenceville, New Jersey
V. Thomas Parker
Department of Biology
San Francisco State University
San Francisco, California
Robert L. Simpson
Vice Chancellor
University of Michigan
Dearborn, Michigan
ACADEMIC PRESS, INC.
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Copyright © 1989 by ACADEMIC PRESS, INC.
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Library of Congress Cataloging-in-Publication Data
Ecology of soil seed banks / edited by Mary Allessio Leck, V. Thomas
Parker, Robert L. Simpson,
p. cm.
Bibliography: p.
Includes index.
ISBN 0-12-440405-7 (hard cover) (alk. paper)
ISBN 0-12-440406-5 (paper cover) ( alk. paper)
1. Soil seed banks. 2. Seeds—Ecology. 3. Vegetation dynamics.
I. Leek, Mary Allessio. II. Parker, V. Thomas. III. Simpson,
Robert L. (Robert Lee), Date.
QK910.E27 198
582'.05'6—ecl9 88-28815
CIP
PRINTED IN THE UNITED STATES OF AMERICA
93 94 95 96 97 98 QW 9 8 7 6 5 4 3 2 1
Contributors
O. W. Archibold Nancy C. Garwood
Department of Geography Department of Botany
University of Saskatchewan Field Museum of
Saskatoon, Saskatchewan Natural History
Canada S7N 0W0 Chicago, Illinois 60605, and
Smithsonian Tropical Research
Herbert G. Baker Institute
Department of Botany Balboa, Panama
University of California
Berkeley, California 94720 Connie Gaudet
Department of Biology
Carol C. Baskin University of Ottawa
School of Biological Sciences Ottawa, Ontario
University of Kentucky Canada KIN 6N5
Lexington, Kentucky 40506
J. P. Grime
Jerry M. Baskin Unit of Comparative Plant
School of Biological Sciences Ecology (NERC)
University of Kentucky Department of Plant Sciences
Lexington, Kentucky 40506 University of Sheffield
Sheffield, England S10 2T
Diane L. Benoit
Agriculture Canada Paul A. Keddy
Research Station, C.P. 457 Department of Biology
S t. -J ean-sur-Richelieu University of Ottawa
Quebec, Canada J3B 6Z8 Ottawa, Ontario
Canada KIN 6N5
Paul B. Cavers
Department of Plant Sciences Victoria R. Kelly
University of Western Ontario Institute of Ecosystem Studies
London, Ontario Mary Flagler Cary Arboretum
Canada N6A 5B7 Millbrook, New York 12545
ix
x Contributors
Paul R. Kemp Kevin J. Rice
Systems Ecology Research Group Department of Agronomy and
College of Sciences Range Science
San Diego State University University of California
San Diego, California 92182 Davis, California 95616
Mary Allessio Leek Bill Shipley
Department of Biology Department of Biology
Rider College University of Ottawa
Lawrenceville, New Jersey 08648 Ottawa, Ontario
Canada KIN 6N5
Svata M. Louda
School of Biological Sciences Robert L. Simpson
University of Nebraska School of Science and
Lincoln, Nebraska 68588 Mathematics
William Paterson College
M. J. McDonnell Wayne, New Jersey 07470
Institute of Ecosystem Studies
The New York Botanical Garden A. G. van der Valk
Mary Flagler Cary Arboretum Department of Botany
Millbrook, New York 12545 Iowa State University
Ames, Iowa 50011
James B. McGraw
Department of Biology Milan C. Vavrek
West Virginia University Department of Biology
Morgantown, West Virginia 26506 West Virginia University
Morgantown, West Virginia 26506
V. Thomas Parker
Department of Biology D. Lawrence Venable
San Francisco State University Department of Ecology and
San Francisco, California 94132 Evolutionary Biology
University of Arizona
Roger L. Pederson Tucson, Arizona 85721
Ducks Unlimited, Inc.
Western Regional Office Irene C. Wisheu
9823 Old Winery Place Department of Biology
Suite 16 University of Ottawa
Sacramento, California 95827 Ottawa, Ontario
Canada KIN 6N5
S. T. A. Pickett
Institute of Ecosystem Studies
The New York Botanical Garden
Mary Flagler Cary Arboretum
Millbrook, New York 12545
Preface
The old adage, 'One year's seeding—seven years' weeding," indicates
that gardeners have long understood the potential of seeds to remain
viable in soil. In recent years many ecologists interested in plant popula­
tion and community dynamics have also come to realize the importance
of seeds in the soil. The soil seed bank refers to seeds and fruits, such as
achenes and caryopses, on or in the soil.
How seeds enter and leave the soil and their persistence are deter­
mined by a variety of factors. These include the seed rain, dispersal,
predation, longevity, and factors controlling germination and recruit­
ment. The importance of these varies with species, and in turn, species
vary in their dependence on persistent seed banks. Some have transi­
tory seed banks, lasting less than a year, whereas others persist in the
soil for decades or perhaps even a millenium or more. Knowledge of the
seed bank dynamics of species that make up a community can provide
an understanding of important limiting factors or processes that occur
within that community. Ultimately, the dynamics of the seed bank guar­
antee the ability of a community to maintain itself and to respond to
change. The reservoir of seeds in soil, the seed bank, may contain di­
verse species, genotypes, and phenotypes that provide substantial flex­
ibility for potential community response.
The ecology of seeds in soils has been considered by Heydecker
(1973), Mayer and Poljakoff-Mayber (1975), Harper (1977), Roberts
(1981), Fenner (1985), and Priestly (1986). A number of basic aspects of
seed ecology have been widely studied, such as seed physiology and
germination (Murray, 1984; Bewley and Black, 1985), dispersal (Murray,
1986), and variations in life history in relationship to seed size or num­
ber (Harper 1977). While this volume provides an update and brings
together much scattered information, it approaches the topic from a
different perspective. We feel that understanding the ecology of seeds is
critical for developing theory on community structure and function.
Our primary objectives are to examine factors influencing seed bank
dynamics and the variety of patterns found among different species. In
xi
xii Preface
addition, we present seed banks in a community context to explore the
ecological implications of different patterns and thus begin the develop­
ment of a synthesis by comparing various communities.
The history of seed bank studies illustrates a disparate and frag­
mented genesis, the result of a multitude of approaches, goals, and
methodological shortcomings. Life history studies of individual species
have provided the basis for understanding the underlying patterns.
In this volume we first examine the general processes that influence
inputs or losses from the seed bank: predation, dormancy/germination
mechanisms, and their evolutionary importance. While we recognize
the importance of dispersal, a manuscript on that topic was not forth­
coming. Fortunately, most chapters touch on dispersal in the context of
seed bank dynamics. Interested readers should consult recent reviews
(e.g., Howe and Smallwood, 1982; Murray, 1986) for more details on
dispersal.
Second, we examine seed banks in a community context. Only eight
vegetation types are included, but the range in diversity of life form,
length of growing season, and dominant environmental conditions al­
low comparisons of seed bank patterns. Finally, the role of seed banks in
vegetation management is examined. In some managed habitats the
goal is elimination of species, e.g., agricultural weeds, whereas in others
the goal is to increase populations, e.g., rare species or those required
for vegetation restoration. The diverse approaches to the study of seed
banks presented by the contributors provide a framework on which to
base generalizations, and provide direction for future studies.
Because we examine processes, specific vegetation types, and man­
agement practices as they relate to the role of seed banks in vegetation
dynamics, this book should be of interest to population and community
ecologists and managers. Moreover, evolutionary consequences of seed
banks should be of interest to population and theoretical biologists.
We thank the contributors for insights regarding methodological
deficiencies on which part of Chapter 1 is based. All indicated the impor­
tance of standardization of techniques; toward this end a working group
should explore the means to bring guidelines to seed bank methods.
We wish to express our gratitude to those who reviewed manu­
scripts, including Susan H. Bicknell, Dwight Billings, Gregory P. Chep-
lick, Laurel R. Fox, Susan Kaliz, Cees M. Karssen, Mark J. McDonnell,
Robert W. Patterson, Steward T. A. Pickett, Francis E. Putz, O. James
Reichman, Kevin J. Rice, J. Stan Rowe, Loren M. Smith, Robert D.
Sutter, Irwin A. Ungar, Arnold G. van der Valk, and Dennis F. Whig-
ham. We are indebted to Florence Sackett for cheerfully keeping up with
typing; Elizabeth Faulkenstein, Linda Feeney, and Richard Deni for
computer assistance; and James H. Carlson. Rider College, William Pa­
terson College, and San Francisco State University supported many as­
Preface xiii
pects of the preparation of this volume. We express our gratitude to
Academic Press, especially Jean Thomson Black and Kerry Pinchbeck.
We especially thank our spouses, Charles F. Leek, Judith D. Parker, and
Penelope Simpson, for their considerable tolerance and understanding.
Mary Allessio Leek
V. Thomas Parker
Robert L. Simpson
Bewley, J. R., and Black, M. (1985). "Seeds: Physiology of Development and Germina­
tion." Plenum Press, New York.
Fenner, M. (1985). "Seed Ecology." Chapman and Hall, London.
Harper, J. L. (1977). "Population Biology of Plants." Academic Press, London.
Heydecker, W., ed. (1973). "Seed Ecology." Pennsylvania State University Press, Uni­
versity Park and London.
Howe, H. F., and Smallwood, J. (1982). Ecology of Seed Dispersal. Annu. Rev. Ecol.
Syst. 13, 201-228.
Mayer, A. M., and Poljakoff-Mayber, A. (1975). "The Germination of Seeds." Mac­
millan, New York.
Murray, D. R., ed. (1984). "Seed Physiology." Vols. 1 and 2. Academic Press, Sydney.
Murray, D. R., ed. (1986). "Seed Dispersal." Academic Press, Sydney.
Priestly, D. A. (1986). "Seed Aging: Implications for Seed Storage and Persistence in the
Soil." Cornell University Press, Ithaca, New York.
Roberts, H. A. (1981). Seed banks in soil. Adv. Appl. Biol. 6, 1-55.
FOREWORD
Seed Banks in
Ecological Perspective
J.P. Grime
Unit of Comparative Plant Ecology (NERC)
Department of Plant Sciences
University of Sheffield
Sheffield, England
I. Introduction
The appearance of this volume signifies that, at last, investigations of
seed and spore banks have become a recognized and indispensable part
of plant ecology. It is salutory to reflect that 59 years lie between this first
synthesis and Ridley's classical work on the dispersal of propagules
(Ridley, 1930). This delay is a measure of the priority which, until re­
cently, spatial patterns have exerted over temporal dynamics in the
minds of plant ecologists.
The recent promotion of seed banks into the foreground of ecologi­
cal theory and practice is therefore one symptom of a major shift in
emphasis toward the analysis of events over time, rather than the detec­
tion of correlations through space, as an approach to understanding the
functioning of populations and communities. This transition has
brought to fruition the work of the pioneers of plant population dy­
namics (e.g., Watt, 1947; Tamm, 1956) and has been interpreted by some
authors (e.g., Harper, 1977, 1982) as a formula for ultimate success in the
attempt to develop generalizing principles in ecology. However, the
ordination of data along temporal, as opposed to spatial, base lines does
not by itself guarantee a sure path to general ecological theory. De­
mography is as capable as cartography of descending into a fragmentary
descriptive exercise when pursued without reference to underlying
principle. Hence, in the specific case of seed bank information, it seems
imperative that demographic analysis is allied to complementary forms
of study. Of particular importance are those which relate the emerging
xv
xvi J.P. Grime
typology of seed banks to the fundamental design constraints which
restrict both ranges and amplitudes in seed form and function. Equally
important, however, is the need to place seed banks securely in relation
to the forms of natural selection that over evolutionary time and in the
generation times of contemporary populations influence the fate of juve­
niles in natural habitats.
II. Origins
The seed banks of arable weeds were among the first to receive intensive
study (Brenchley, 1918), and their role in the rapid exploitation of dis­
turbed ground achieved public recognition when the Flanders poppy
(Papaver dubium) was adopted as a memorial symbol for those who fell
on the cratered battlefields of World War I. The presence of substantial
numbers of dormant seeds in the soil has been detected in a wide range
of other habitats, including some occupied by a closed cover of perennial
vegetation. Especially notable contributions include those of Darwin
(1859), Milton (1939), Gomez-Pompa (1967), and Marks (1974), all of
whom recognized that the presence of a reserve of dormant seeds con­
ferred the potential for population recovery following disturbance of the
established vegetation.
Until recently the characterization of seed banks mainly consisted of
attempts to determine whether particular species developed persistent
seed banks in the soil. This usually involved a census of buried dormant
seeds conducted at one occasion; in the majority of studies viable seeds
were detected through the appearance of seedlings during laboratory
incubation of soil samples, but several investigations (e.g., Kropäc, 1966;
Major and Pyott, 1966) assumed heroic proportions through the commit­
ment of the authors to the task of recovering and identifying all living,
ungerminated seeds by extremely tedious fractionating procedures.
Seed persistence has been demonstrated also by examination of the
viable seed content of soil samples from beneath buildings of known
antiquity (0dum, 1965) and by experimental burials of seeds, followed
by germination tests on samples exhumed at various intervals (Darling­
ton and Steinbaur, 1961).
The decade 1970-1980 coincided with a growing appreciation of the
critical importance of regeneration mechanisms in the functioning of
plant populations and the structuring of plant communities. It was soon
apparent that the objectives in both of these fields of inquiry could not
be met by a simple dichotomy between plants which were capable and
those which were incapable of long-term seed persistence.
Seed Banks in Ecological Perspective xvii
III. Seed Bank Classification
A critical step in the development of a more sophisticated typology of
seed banks was the completion of studies in which the fate of seeds was
monitored by programs of surface soil sampling at frequent intervals
throughout the year. In the investigation of Sarukhän (1974), for exam­
ple, this approach allowed quantitative assessments of seed longevity
and turnover in the seed banks of three coexisting pasture species of
Ranunculus, and it was possible to incorporate the seed bank data into
models representing the population dynamics of each species. In a more
comprehensive but less detailed study, Thompson and Grime (1979)
measured seasonal variation in the densities of germinable seeds in 10
contrasting habitats. As in many earlier investigations, few consistent
relationships were found between the density of buried seeds exhibited
by a species and its abundance in the community of established plants.
More significant, however, was the recognition that seasonal patterns in
the density of germinable seeds observed in various communities fell
into four basic types that were consistent with the morphology and
germination characteristics of seeds examined in the laboratory (Fig. 1).
This study, in attempting a general linkage between seed bank type
and germination physiology, built upon a number of pioneering studies,
such as those of Went (1949), Ratcliffe (1961), Vegis (1964), and Wesson
and Wareing (1969a). In retrospect, the lack of interaction between ecolo­
gists and germination physiologists, which persisted well into the 1970s,
can now be viewed as one of the most puzzling examples of missed
opportunities in the checkered history of biological science; all of the
physiological phenomena that are now crucial to a mechanistic under­
standing of seed banks (e.g., afterripening, chilling requirements, light
requirements, responses to fluctuating temperatures, canopy-induced
dormancy) had been the subject of intensive study over many years
prior to the development of a seed bank classification.
The classification in Fig. 1 is lacking in subtlety, but has the merit
that logical connections can be established with major factors influenc­
ing the fate of juveniles. It also enables seed bank types to be placed in
relation to other regenerative strategies (Table 1), such as vegetative
expansion and the capacity to develop a bank of persistent seedlings. At
this relatively crude level of classification, it is also possible to explore
the parallels between seed banks and comparable phenomena in various
heterotrophs, including fungi, insects, and fish (Wourms, 1972). This is
not to suggest, however, that seed bank classification should not be
further elaborated; several attempts have been made already (e.g.,
Roberts, 1981; Grime, 1981), and there is opportunity for further refine-