Mechanisms of Forest Response to Acidic Deposition

250 Pages·1990·14.461 MB·English

by  Alan A. Lucier, Sharon G. Haines (auth.), Alan A. Lucier, Sharon G. Haines (eds.)

Mechanisms of Forest Response
to Acidic Deposition
Alan A. Lucier Sharon G. Haines
Editors
Mechanisms of Forest Response
to Acidic Deposition
With 12 illustrations
Springer-Verlag
New York Berlin Heidelberg
London Paris Tokyo Hong Kong
ALAN A. LUCIER SHARON G. HAINES
Flesearch ~orester Soils Flesearch Section Leader
NCASI International Paper
New York, NY 10016, USA Bainbridge, GA 31717, USA
Library of Congress Cataloging-in-Publication Data
Mechanisms of forest response to acidic deposition/Alan A. Lucier,
Sharon G. Haines, editors.
p. cm.
Includes bibliographical references.
ISBN-13:978-1-4612-7982-2 (alk. paper)
1. Trees-Effect of acid deposition on. 2. Forest ecology.
3. Trees-Nutrition. 4. Soil ecology. I. Lucier, Alan Alfred,
1984- . II. Haines, Sharon.
SB745.4.M43 1990
581.5'2642-dc20 89-48303
Printed on acid-free paper.
© 1990 Springer-Verlag New York Inc.
Softcover reprint of the hardcover 1st edition 1990
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9 8 7 6 5 4 3 2 1
ISBN-13:978-1-4612-7982-2 e-ISBN-13:978-1-4612-3364-0
DO I: 10.1007/978-1-4612-3364-0
Preface
This volume addresses several key mechanisms by which forest ecosys
tems might respond to acidic deposition. These mechanisms have been
identified in numerous research papers and general review articles during
the past decade. The reviews presented here take the next step by ana
lyzing the mechanisms in detail and developing specific recommendations
for further research.
We have not attempted to provide a comprehensive treatment of acidic
deposition and forest ecosystems. The strength of this volume lies in its
in-depth treatment of selected technical issues, in the extensive lists of
citations, and especially in the insights provided by the authors of the
individual chapters. The book is intended for professionals and graduate
students in soil science, forest ecology, and environmental science. It will
also be of use to environmental policy makers and forest managers who
need to understand technical issues affecting assessments of acidic dep
osition and its effects on natural resources.
A key mechanism not specifically addressed in this volume is acceler
ated leaching of basic nutrient cations from soils. This mechanism has
been reviewed by J.O. Reuss and D.W. Johnson in their authoritative
book Acid Deposition and the Acidification ofS oils and Waters (Springer
Vedag 1986). Reuss and Johnson identified mineral weathering rate as an
important uncertainty in their analysis. This uncertainty is analyzed in
detail here by G.N. White, S.B. Feldman, and L.W. Zelazny in Chapter 4.
Funding for the reviews in this volume was provided by the National
Council of the Paper Industry for Air and Stream Improvement (NCASI).
The review topics were selected during initial planning of NCASrs Air
Quality/Forest Health Program by a work group of soil scientists from
U.S. forest products companies. We extend special thanks to Dr. Nicholas
Berenyi of Westvaco Corp. and Mr. Anthony Filauro of Great Northern
Paper -Company for valuable contributions to this project from start to
finish.
ALAN A. LUCIER
SHARON G. HAINES
v
Contents
Preface ........... " . . . . . . . . .. . . . . .. . . . . . . . . .. . . . . . v
Contributors ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
1. Overview and Synthesis
ALAN A. LUCIER and SHARON G. HAINES.. .. .. .. . . .. . . . 1
2. Evaluation of Dry Deposition, Pollutant Damage, and
Forest Health with Throughfall Studies
GEOFFREY G. PARKER ............................. 10
3. Effects of Acidic Deposition on the Chemical Form and
Bioavailability of Soil Aluminum and Manganese
JEFFREY D. WOLT ................................ 62
4. Rates of Nutrient Release by Mineral Weathering
G. NORMAN WHITE, STEVEN B. FELDMAN, and
LUCIAN W. ZELAZNY .............................. 108
5. Effects of Acidic Deposition on Soil Organisms
DAVID D. MYROLD ................................ 163
6. The Atmosphere and the Rhizosphere: Linkages with
Potential Significance for Forest Tree Health
WILLIAM H. SMITH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 188
Index ............................................ 243
vii
Contributors
STEVEN B. FELDMAN, Research Associate, Department of Crop and Soil
Environmental Sciences, Virginia Polytechnic Institute and State Uni
versity, Blacksburg, Virginia 24061, USA.
SHARON G. HAINES, Leader of the Soils Research Section, International
Paper, Bainbridge, Georgia 31717, USA.
ALAN A. LUCIER, Research Forester, National Council of the Paper In
dustry for Air and Stream Improvement (NCASI), New York, New York
10016, USA.
DAVID D. MYROLD, Associate Professor, Department of Soil Science,
Oregon State University, Corvallis, Oregon 97331-2213, USA.
GEOFFREY G. PARKER, Forest Ecologist, Smithsonian Environmental Re
search Center, Edgewater, Maryland 21037-0028, USA (formerly with
the New York Botanical Garden's Institute of Ecosystem Studies).
WILLIAM H. SMITH, Professor of Forest Biology, School of Forestry and
Environmental Studies, Yale University, New Haven, Connecticut
06511, USA.
G. NORMAN WHITE, Research Associate, Department of Crop and Soil
Environmental Sciences, Virginia Polytechnic Institute and State Uni
versity, Blacksburg, Virginia 24061, USA.
JEFFREY D. WOLT, Project Leader, Environmental Soil Chemistry, For
mulations and Environmental Chemistry Department, Dow Elanco,
Midland, Michigan 48641-1706, USA.
LUCIAN W. ZELAZNY, Professor, Department of Crop and Soil Environ
mental Sciences, Virginia Polytechnic Institute and State University,
Blacksburg, Virginia 24061, USA.
ix
1
Overview and Synthesis
ALAN A. LUCIER and SHARON G. HAINES
I. Introduction
Acidification of forest ecosystems is a complex process controlled by nu
merous hydrologic, geochemical, and biological factors. In the context of
soil genesis, acidification is a normal consequence of mineral weathering,
biological activity, and base cation leaching in humid environments (pre
cipitation exceeds evapotranspiration). Relevant time scales are decades
to millenia. In the context of ecology and environmental science, acidi
fication may result from biomass harvest, land use conversions, natural
changes in vegetation, and intentional or unintentional inputs of acidi
fying compounds, especially those of sulfur and nitrogen. Relevant time
scales range from days to centuries.
Atmospheric inputs of acidifying compounds derived from fossil fuel
combustion are commonly known as acidic deposition or "acid rain." In
many parts of the world, acidic deposition measurably alters the chem
istry of solutions in forest ecosystems. Annual proton inputs by wet and
dry acidic deposition exceed net proton production by natural processes
at some sites (van Breemen et al. 1984). The capacity offorest ecosystems
to buffer acid inputs is great, however, and the extent and magnitude of
ecological effects are unknown. The numerous factors that control eco
system response to acid inputs vary greatly in space and time and interact
in ways which are not fully understood. Effects of acidic deposition are
subtle, and methods for their measurement are still under development.
Numerous reviews and assessments of acidic deposition's potential im
pacts on forests have been published (e.g., Abrahamsen 1980, Kulp 1987,
Morrison 1984, Rehfuess 1981). Available data suggest that ambient rain
fall acidity does not visibly damage foliage or reduce tree growth. Ques
tions remain about the potential for direct injury of tree tissues by other
mechanisms. These include acid toxicity to reproductive structures and
sensitive life stages (Cox 1983, Percy 1986); erosion of cuticle by long
term exposure to wet and dry acidic deposition (Huttunen and Laine
1983, Percy and Baker 1987); and foliar injury caused by highly acidic
2 A.A. Lucier and S.G. Haines
solutions deposited as liquid aerosols (e.g., fog) or formed on vegetation
surfaces by dissolution of accumulated dry-deposited acids (Jacobson
1984). Well-designed experiments could determine the potential signifi
cance of these mechanisms within 5 to 10 years. Possible interactions of
acidic deposition with other stresses pose a more formidable problem
(Huttunen 1984, Laurence 1981).
Scientific opinion is extremely divided regarding potential impacts of
acidic deposition on forest element cycles and tree nutrition. Theoretically
sound mechanisms of impact have been described, but no consensus
exists as to their importance as determinants of forest health and pro
ductivity. Frequently mentioned mechanisms include:
(a) Accelerated leaching of base cations from soils and foliage, leading to
nutrient deficiency or imbalance.
(b) Increased mobilization of aluminum and other metals, leading to root
damage, nutrient deficiency, and reduced drought tolerance.
(c) Inhibition of soil biological processes, leadi'ng to reduced organic mat
ter decomposition, nutrient deficiency, damage to mycorrhizae, and
altered host-pathogen relationships.
(d) Increased bioavailability of nitrogen, leading to accelerated organic
matter decomposition and increased tree susceptibility to natural
stresses. Increased tree susceptibility to stress may occur as a conse
quence of changes in growth rate, phenology, carbon allocation, nu
trition, and water relationships.
The importance of these mechanisms is uncertain because knowledge of
rates, interactions, and variability of biogeochemical and hydrologic proc
esses is incomplete.
The five literature reviews in this volume explore several important
uncertainties about the potential effects of acidic deposition on forest
element cycles and tree nutrition. The following paragraphs present the
rationale for topic selection and a brief summary of findings within each
review.
A. Foliage Leaching
When rain comes in contact with the leaves and branches of a forest
canopy, the chemistry of the rainwater changes; solutes pass from rain
to plant tissues and vice versa. In addition, particles deposited on canopy
surfaces before rainfall events may be dissolved or physically displaced.
The "throughfall" solutions that ultimately reach the ground may bear
little chemical resemblance to incoming rain.
Throughfall has been studied for many years and is recognized as an
important pathway in forest nutrient cycles. More recently, throughfall
has been studied in investigations of regionally distributed air pollutants
and their possible effects on forest health. Some investigators are deveI-
1. Overview and Synthesis 3
oping throughfall measurement techniques for quantifying dry acidic dep
osition to forest canopies. Other investigators are measuring throughfall
chemical fluxes to determine pollutant effects on the leaching of nutrients
and organic metabolites from foliage.
In Chapter 2, Dr. Geoffrey Parker reviews the extensive literature on
characteristics of throughfall in forest ecosystems. He describes in detail
the physical and biological processes that control throughfall chemistry
and discus"Ses hypothesized and observed effects of acidic deposition and
other pollutants on throughfall composition. Available evidence suggests
that pollutant effects on nutrient losses from foliage are small. Additional
experimentation and methods development are required, however, to (a)
determine possible long-term pollutant exposure effects on nutrient losses
and (b) evaluate the utility of throughfall analyses for monitoring dry
deposition and forest health.
B. Aluminum Mobilization
Although annual atmospheric inputs of protons are small compared to
proton quantities in soils, acidic deposition does affect current soil chem
istry (see Ruess and Johnson [1986] for an excellent review and synthesis).
Deposition of sulfate and other ions can increase the ionic strength of
soil solutions and thus increase soil solution acidity and aluminum con
centrations through the "salt effect". In addition, "mobile anions" in
acidic deposition (especially SO/-) tend to move through soil profiles,
thus promoting the co-leaching of cations. Mobile anion leaching may
increase the net rate of base cation loss and reduce soil base saturation.
Potential soil chemistry effects vary greatly among sites depending on
rates of atmospheric deposition and numerous properties of soils and
vegetation (Wiklander and Andersson 1971).
Increased bioavailability of soil aluminum and manganese is a potential
consequence of acidic deposition's effects on soil chemistry. Aluminum
and manganese are ubiquitous components of soils. In alkaline and cir
cumneutral soils, aluminum and manganese exist primarily in solid
forms. In acidic soils, however, substantial amounts of aluminum and
manganese may be dissolved in soil solutions and available to plant roots.
It is well established that high aluminum and manganese concentrations
in soil solutions can damage sensitive crop plants. Farmers often apply
lime to raise soil pH and thus reduce dissolved aluminum and manganese
species to safe levels.
Although forest soils are often quite acidic, widespread aluminum and
manganese toxicity to forest trees has generally been considered unlikely.
The law of natural selection and the usual nonresponsiveness of tree
growth to lime applications (Bengtson 1968) indicate that most forest tree
species are well adapted to the naturally acidic soils they occupy. Recent
concerns about acidic deposition and forest decline have challenged this
4 A.A. Lucier and S.G. Haines
traditional view, however. Some investigators have proposed that acidic
deposition can increase soil acidity substantially and thus raise available
aluminum and manganese to root-damaging levels.
In Chapter 3, Dr. Jeffrey Walt reviews soil chemical and biological
relationships relevant to possible effects of acidic deposition on forests
through the mechanism of increased availability of aluminum and man
ganese. Aluminum and manganese toxicity are manifestations of "acid
soil infertility", a complex phenomenon that may concurrently cause
deficiencies in essential plant nutrients. Although forest trees appear to
be tolerant to levels of aluminum and manganese found in most forest
soil solutions, few studies have specifically addressed this concern. The
most useful assessment criterion is likely to be the relationship of root
elongation rate to activities of toxic chemical species in hydroponic or
soil solutions. Future monitoring studies should better define spatial and
temporal relationships between root function and concentrations of alu
minum and manganese species in soil solutions. Future experimental
work should determine how tree responses to aluminum and manganese
are affected by ratios of elements in soil solutions and other environ
mental conditions.
C. Mineral Weathering
Implications of acidic deposition for forest health and productivity are
uncertain because of inadequate knowledge of forest element cycles and
tree nutrition. Investigations now underway at several sites are quantifying
acidic deposition, nutrient uptake by vegetation, nutrient leaching from
soils and foliage, and tree responses to changes in soil chemistry.
Although many information gaps are being filled, new methods are
needed to quantify several processes by which forest ecosystems may
resist accelerated acidification. Most notable of these processes is mineral
weathering. Weathering reactions can buffer hydrogen ion inputs and
replace base cations lost by leaching. Moreover, weathering reaction rates
may increase in response to acid inputs and thus compensate for depo
sition-induced accelerations in acidification processes. Models that con
sider only cation exchange and aluminum hydrolysis as acid-buffering
mechanisms may overstate potential adverse effects on sites where active
weathering is occurring. Potential effects of acidic deposition on forest
soil fertility and tree nutrition cannot be accurately assessed without bet
ter understanding of rates of nutrient release by weathering.
Dr. G. Norman White, Steven B. Feldman, and Professor Lucian W.
Zelazny review weathering mechanisms and the factors that control
weathering rates in Chapter 4. They identify many technical obstacles
that have hindered field and laboratory investigations and conclude that
a satisfactory approach to weathering rate estimation has not yet been
developed. Development of a satisfactory approach requires basic re-