Preface to the Second Edition
vii
are the best way to resolve this problem so that misinterpretations do not
occur. For those interested only in exchanges with flat leaves, the development in this book may seem somewhat more complicated. However, "flat
leaf' versions of the equations are easy to write and when interest extends
to nonilat objects this analysis will be fully appreciated. When extending
energy budgets to canopies we suggest herni-surface area, which is onehalf the surface area. For canopies of flat leaves, the hemi-surface area
index is identical to the traditional leaf area index; however for canopies
of nonflat leaves, such as conifer needles, the hemi-surface area index is
unambiguous while "projected" leaf area index depends on many factors
that often are not adequately described.
One convention that remains the same as the first edition is the use
of J k g for water potential. Although pressure units (kPa or MPa) have
become popular in the plant sciences, potential is an energy per unit mass
and the J/kg unit is more fundamental and preferred. Fortunately, J k g
and kPa have the same numerical value so conversions are simple.
As with the previous edition, many people contributed substantially
to this book. Students in our classes, as well as colleagues, suggested
better ways of presenting material. Several publishers gave permission
to use previously published materials. Marcello Donatelli checked the
manuscript for errors and prepared the manuscript and figures to be sent
to the publisher. The staff at Springer-Verlag were patient and supportive
through the inevitable delays that come with full schedules. We are also
grateful to our wives and families for their help and encouragement in
finishing this project. Finally, we would like to acknowIedge the contributions of the late Champ B. Tanner. Most of the material in this book was
taught and worked on in some form by Champ during his years of teaching and research at University of Wisconsin. Both of us have been deeply
influenced by his teaching and his example. We dedicate this edition to
him.
G. S. Campbell
J. M. Norman
Pullman and Madison, 1997
vii
are the best way to resolve this problem so that misinterpretations do not
occur. For those interested only in exchanges with flat leaves, the development in this book may seem somewhat more complicated. However, "flat
leaf' versions of the equations are easy to write and when interest extends
to nonilat objects this analysis will be fully appreciated. When extending
energy budgets to canopies we suggest herni-surface area, which is onehalf the surface area. For canopies of flat leaves, the hemi-surface area
index is identical to the traditional leaf area index; however for canopies
of nonflat leaves, such as conifer needles, the hemi-surface area index is
unambiguous while "projected" leaf area index depends on many factors
that often are not adequately described.
One convention that remains the same as the first edition is the use
of J k g for water potential. Although pressure units (kPa or MPa) have
become popular in the plant sciences, potential is an energy per unit mass
and the J/kg unit is more fundamental and preferred. Fortunately, J k g
and kPa have the same numerical value so conversions are simple.
As with the previous edition, many people contributed substantially
to this book. Students in our classes, as well as colleagues, suggested
better ways of presenting material. Several publishers gave permission
to use previously published materials. Marcello Donatelli checked the
manuscript for errors and prepared the manuscript and figures to be sent
to the publisher. The staff at Springer-Verlag were patient and supportive
through the inevitable delays that come with full schedules. We are also
grateful to our wives and families for their help and encouragement in
finishing this project. Finally, we would like to acknowIedge the contributions of the late Champ B. Tanner. Most of the material in this book was
taught and worked on in some form by Champ during his years of teaching and research at University of Wisconsin. Both of us have been deeply
influenced by his teaching and his example. We dedicate this edition to
him.
G. S. Campbell
J. M. Norman
Pullman and Madison, 1997