Table Of ContentMacroclimate and plant forms:
An introduction to predictive modeling
in phytogeography
Tasks for vegetation science 1
Series Editor
HELMUT LIETH
University of Osnabriick, F.R. G.
ELGENE OWEN BOX
Macroclimate and plant forms:
An introduction to predictive modeling
in phytogeography
DR W. JUNK PUBLISHERS THE HAGUE/BOSTON/LONDON 1981
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Library of Congress Cataloging in Publication Data
Box, Elgene O.
Macroclimate and plant forms.
(Tasks for vegetation sciences; I)
Bibliography: 16 pp.
I. Vegetation and climate-Mathematical models. 2. Phyto
geography-Mathematical models. 3. Prediction theory.
I. Title. II. Series.
QK754.5.B69 581.5'42 81-12368
AACR2
ISBN-l3: 978-94-009-8682-4 e-ISBN-13: 978-94-009-8680-0
DOl: lO.l007/978-94-009-8680-0
Cover design: Max Velthuijs
Copyright @ 1981 Dr W. Junk Publishers, The Hague.
Softcover reprint of the hardcover I st edition 1981
All rights reserved. No part of this publication may be reproduced. stored in a retrieval system. or transmitted in any form
or by any means. mechanical. photocopying. recording. or otherwise. without the prior written permission of the publishers
Dr W. Junk Publishers. P.O. Box 13713. 2501 ES The Hague. The Netherlands.
Preface by the T: VS Series editor
The first volume of any scientific book series is always something special. Long deliberations and negotiations
have finally borne fruit. A new scientific series, Tasks for Vegetation Science, presents itself with the first 3
volumes almost simultaneously, setting in content and format standards for the books to come. Volumes I and
3 deal with modelling attempts ofthestructure and function of vegetation. Volume I, this volume, contains the
attempt to predict vegetation structure from various climatic parameters. This book will probably serve as a
milestone in the long list of previous attempts to correlate vegetation structures with climatic parameters.
Aridity indices, EP-values, bioclimatic thresholds of various sorts have been tried in the past with increasing
success to predict vegetation types.
All these attempts were oflimited value, however, since considerable margins of uncertainties or exceptions
for greater portions ofthe world remained. Previous workers in this field together with the many critics always
demanded better solutions after they had presented their models. They demanded better data for
meteorological observations, closer networks for vegetation data, the inclusion of more environmental
parameters, better systems for vegetation classification to name only a few.
It was therefore a noteworthy attempt of Dr. Box to select such a difficult task for his thesis. Dr. Box, a
mathematiCian by early training, possessed the mathematical tools seldom available to a vegetation
scientist to undertake a new attempt towards the prediction of vegetation structure from environmental,
climatic parameters.
Since our time has generally better information than our colleagues in the past, it is only natural that we try
to model relations between vegetation parameters and environmental parameters more precisely, if such
relations, indeed, exist.
To show the vegetation types, geographical areas, and parameters where such relations exist and where they
do not or only weakly exist was the purpose of Dr. Box' study. His approach has entered a new field of numeric
vegetation modelling, the use of information systems. Since the approach is the first of its kind in vegetation
science, one cannot expect perfection in the predictive power of his model set. However, the new method once
presented is open for discussion, for refinement and for intensive testing.
For the series editor it is especially gratifying to present the volume as the first one in a row of volumes with
similar tasks. The author ofthis book worked for a longtime together with the series editor while he developed
the basic structure of his information system called 'ECOSIEVE'.
Once perfect, the predictive power of this model has consideraple theoretical and practical value for
management purposes and is therefore very timely in its appearance. As an intensive study, combining skills in
vegetation science and mathematics and computer science, it will certainly set an example for the next student
generation of vegetation science. The use of information systems as well as multifactorial regression analysis
has just begun to yield results in vegetation analyses of various kinds. Our plan is to present in future volumes of
this series more new techniques and concepts of this kind useful for our science to the vegetation scientists.
V
Volume 3, by Dr. Ross, dealing with biophysical modelling on ecosystems, is already in print. Several more
books, presenting new methods and special treatments of important ecosystems, are in various stages of
completion.
With the first volume appearing, the new series T: VS is on its way. It is our hope that the series will serve our
profession in the future and that the first volume will have a good start.
Osnabruck, March 1981 H. Lieth
VI
Foreword
This study arose out ofthe old question of what actually determines vegetation structure and distributions. Is
climate the overriding control, as one would suppose from reading the more geographically oriented
literature? Or is climate only incidental, as suggested by more site and/ or taxon-oriented writers? The
question might be phrased more realistically: How much does climate control vegetation processes,
structures, and distributions?
It seemed to me, as an ambitious doctoral student, that one way to attempt an answer might be to try to
predict world vegetation from climate alone and then compare the predicted results with actual vegetation
patterns. If climatic data were sufficient to reproduce the world's actual vegetation patterns, then one could
conclude that climate is the main control. This book represents an expanded, second-generation version of
that original thesis. It presents world-scale vegetation and ecoclimatic models and a methodology for
applying such models to predict vegetation and for evaluating model results. This approach also provides a
means of geographical simulation of vegetation patterns and changes, which represent necessary data inputs
in other fields such as atmospheric chemistry and biogeochemical cycling.
It has been fairly well accepted that climatic and other environmental conditions are associated with the
evolution of particular aspects of plant form (convergent evolution). The particular configurations of plant
size, photosynthetic surface area and structure (e.g. sclerophylly, stomatal 'resistance'), and their seasonal
variations represent what one can recognize fairly readily as distinct growth forms. These aspects of form,
however, also determine the potential rates and annual totals of photosynthesis, respiration and water loss of
plants and thereby set the climatic limits on their water and energy budgets and thus their distributional limits
in the real world. This logic is perhaps best called 'ecophysiognomic' and can be stated as an initial hypothesis:
Plant form and structure are evolutionary results of climate (among other factors) but also largely
determine the current distributions and viability of plants through their effects on plant water and
energy budgets.
If true, this implies both an ecology and a biogeography at the level of plant life forms - a fundamentally
ecological life-form approach to vegetation, which not only should provide new insights and conceptual tools
but perhaps also make vegetation study and appreciation somewhat more accessible to those without special
training in botanical Latin and taxonomy.
The study presented herein represents an attempt to discern world patterns in the relationship between
plant form and vegetation structure (physiognomy and morphology) on the one hand and environmental,
mainly climatic conditions on the other. The focus is on plant water and energy budgets and how they and
related physiological processes are related to and limited by climatic conditions (in different types of climates)
working through the particular combinations of form characters represented by different plant life forms.
The project attempts to organize much detail and many smaller explanations into a world-scale framework
and initial empirical model, as the basis for subsequent, more analytical work on relations between plant form
VII
and physiological limits. The proposed world set of plant life forms is related to climate by means of climatic
envelopes, which are used with a world climatic data-base to predict world life-form distributions. These are
interpreted as vegetation types and compared with actual vegetation patterns and site data, with generally
good results. (The validation suffers some from insufficient descriptions of local vegetation which also
provide climatic data. Readers are invited to send local vegetation and climatic data for comparison with
predicted vegetation profiles.)
As the title states, the book is intended as an introduction. In developing the vegetation classification the
first criterion was to cover the main types of terrestrial plants in the world (but not necessarily all taxa). In
describing climate the main emphasis was on covering the most important ecological aspects. For sake of
manageability, both vegetation and climate had to be described with as few units as possible. Since the
purpose is to discern basic, general relationships, if they exist, sweeping generalizations and simplifications
are sometimes made. These are then pushed as far as possible in the modeling in order to see where they break
down when exposed to the full range of variation in earth's climatic conditions. Criticism is expected. Only by
this sort of generalization, however, can one put together a world-scale model which can be expected to
answer general questions. The model represents perhaps the first serious attempt to predict fairly detailed
vegetation profiles, including seasonal aspects, and distributions for all parts of the world's land area. It is
also probably one of the first vegetation studies, at any geographic scale, to compare predicted and actual
vegetation profiles rigorously as a means of assessing model accuracy and thus the validity (and adequacy) of
the underlying assumptions.
The study draws on several sources and methods which are not commonplace in traditional American
botany and plant ecology (as judged at least by recent journal articles). Among these are a comparative,
geographic outlook over large areas (involving literature in other languages); a fairly rigorous quantitative
approach (involving necessarily large amounts of climatic data); a focus on life forms as the fundamental
plant unit (providing better ecological and physiognomic resolution); geographical and mathematically
&imple ecological modeling; and rigorous scrutiny of predicted results. The result of this synthesis is a
quantitative geographical methodology which can be used both for simulation! prediction and as a
geographic alternative and complement to traditional statistical hypothesis-testing. It nevertheless represents
an approach which must be superficial, at least initially, and which requires further development and
improvements.
This book is dedicated to Heinrich Walter for his many and enormous conceptual and geographic
contributions to the ecological study of world vegetation; and to Helmut Lieth, who made the author's
admission to doctoral study in ecology at an American university possible, provided early guidance, and
encouraged the development of latent world-scale interests. Special thanks is also due the Kernforschungs
anlage (Nuclear Research Center) in lillich, Germany, where much of the computerized basis for this and
other research was initially developed. Work in lillich and Hohenheim (with Walter) also permitted the
author to observe many vegetation types of Europe, North Africa and Atlantic islands which could not have
been visited otherwise. (More extensive ecological study during 1981-82 in the Old and New World tropics is
anticipated.) Grateful acknowledgement is due the computer center of the University ofN orth Carolina, and
also those of Duke University and the University of Georgia, for computing time and other assistance; and to
the UNC Photographic Laboratory for photography of the largest computer maps.
The manuscript was typed by the superb office staff at the University of Georgia geography department:
Pat Wall, Mildred Bell, Anne Berryman, Kathy Smith, Sharon Mullins, Dawn Tolbert, and Sue Werner,
under the direction of Yvonne Pommerville, office manager. No department ever had a more helpful office
staff.
Most importantly, this project would not have been even remotely possible without the perseverance ofthe
author's wife, who worked rotating shifts to provide daily transportation, all living expenses, and some
school expenses while the author was a doctoral student.
Athens (Georgia), 31 May 1981 Elgene Owen Box
VIII
Contents
Preface by the T: VS Series editor / v
Foreword/ vii
List of ta bles / xi
List of world maps/ xiii
Chapter 1. Introduction/ 1
Chapter 2. Modeling ecological structure and function/5
A. World vegetation models in general/5
B. The current model/6
C. Model structure and technical considerationsf7
Chapter 3. Ecological classification of world vegetation/ II
A. Vegetation description and vegetation data/II
B. Ecophysiognomic characters of terrestrial vegetation/ 15
C. Life forms of world terrestrial vegetation/20
Chapter 4. Modeling the effective environment/27
A. Climate data/27
B. Selection of ecoclimatic variables/29
C. The ecoclimatic variables and their significance/31
Chapter 5. The ecological model: life-form limitation, cover and dominance/33
A. Ecological data/33
B. The environmental-limitation model/34
C. The cover model/42
D. The dominance model/42
E. Proximity to environmentallimits/44
F. Interpreting vegetation formations/45
IX
Chapter 6. Model results/47
A. Model output and applicability/47
B. Generating and mapping world results/50
C. Overview of world ecoclimates/52
D. Life-form prediction frequency /64
E. Predicted plant-form distributions/64
F. Predicting world vegetation types/94
G. Physiognomic diversity of vegetation/94
H. General observations and problems/ 101
Chapter 7. Evaluation of model results/ 103
A. Site comparison of predicted and actual vegetation/ 103
B. Vegetation and climate at unusual sites/ 122
C. Vegetation sensitivity to climatic variation/ 123
Chapter 8. Conclusions and next steps/ 129
APPENDICES
Appendix A. Description of the plant types/ 133
Appendix B. Predicted vegetation at selected representative and well-known sites/ 175
Appendix C. Predicted vegetation at the validation sites/ 199
Appendix D. Actual vegetation at the validation sites/2l9
Appendix E. The macroclimatic data-base/235
Appendix F. The processing and mapping programs/237
References/243
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