An introduction to environmental biophysics gaylon s campbell, john m norman
Gaylon S. Campbell John M. Norman An Introduction to Environmental Biophysics Second Edition With 8 1 Illustrations Springer Gaylon S. Campbell Decagon Devices, Inc. 950 NE Nelson Ct. Pullman, WA 99163 USA John M. Norman University of Wisconsin College of Agricultural and Life Sciences Soils Madison, WI 53705 USA Library of Congress Cataloging - in - Publication Data Campbell, Gaylon S. Introduction to environmental biophysics/G. S. Campbell, J. M. Norman. 2nd ed. p. cm. Includes bibliographical references and index. ISBN 0 - 387 - 94937 - 2 (softcover) 1. Biophysics. 2. Ecology. I. Norman, John M. 11. Title. CH505.C34 1998 571.4-dc2 1 97 - 15706 Printed on acid - free paper. O 1998 Springer - Verlag New York, Inc. All rights resewed. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer - Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analy - sis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as under - stood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by any - one. Production coordinated by Black Hole Publishing Services, Berkeley, CA, and managed by Bill Imbornoni; manufacturing supervised by Johanna Tschebull. Typset by Bartlett Press, Marietta, GA. Printed and bound by Edwards Brothers, Inc., Ann Arbor, MI. Printed in the United States of America. 9 8 7 6 5 4 3 2 (Corrected second printing, 2000) ISBN 0 - 387 - 94937 - 2 SPIN 10768147 Springer - Verlag New York Berlin Heidelberg A member of BertelsrnannSpringer Science+Business Media GmbH Preface to the Second Edition The objectives of the first edition of " An Introduction to Environmental Biophysics " were " to describe the physical microenvironment in which living organisms reside" and " to present a simplified discussion of heat and mass transfer models and apply them to exchange processes between organisms and their surroundings." These remain the objectives of this edition. This book is used as a text in courses taught at Washington State University and University of Wisconsin and the new edition incorporates knowledge gained through teaching this subject over the past 20 years. Suggestions of colleagues and students have been incorporated, and all of the material has been revised to reflect changes and trends in the science. Those familiar with the first edition will note that the order of pre - sentation is changed somewhat. We now start by describing the physical environment of living organisms (temperature, moisture, wind) and then consider the physics of heat and mass transport between organisms and their surroundings. Radiative transport is treated later in this edition, and is covered in two chapters, rather than one, as in the first edition. Since remote sensing is playing an increasingly important role in environmen - tal biophysics, we have included material on this important topic as well. As with the first edition, the ha1 chapters are applications of previously described principles to animal and plant systems. Many of the students who take our courses come from the biolog - ical sciences where mathematical skills are often less developed than in physics and engineering. Our approach, which starts with more de - scriptive topics, and progresses to topics that are more mathematically demanding, appears to meet the needs of students with this type of back - ground. Since we expect students to develop the mathematical skills necessary to solve problems in mass and energy exchange, we have added many example problems, and have also provided additional problems for students to work at the end of chapters. One convention the reader will encounter early in the book, which is a significant departure from the first edition, is the use of molar units for mass concentrations, conductances, and fluxes. We have chosen this unit convention for several reasons. We believe molar units to be fundamen - tal, so equations are simpler with fewer coefficients when molar units Preface to the Second Edition are used. Also, molar units are becoming widely accepted in biological science disciplines for excellent scientific reasons (e.g., photosynthetic light reactions clearly are driven by photons of light and molar units are required to describe this process.) A coherent view of the connectedness of biological organisms and their environment is facilitated by a uniform system of units. A third reason for using molar units comes from the fact that, when difisive conductances are expressed in molar units, the numerical values are virtually independent of temperature and pressure. Temperature and pressure effects are large enough in the old system to require adjustments for changes in temperature and pressure. These tem - perature and pressure effects were not explicitly acknowledged in the first edition, making that approach look simpler; but students who delved more deeply into the problem found that, to do the calculations correctly, a lot of additional work was required. A fourth consideration is that use of a molar unit immediately raises the question "moles of what? " The dependence of the numerical value of conductance on the quantity that is diffusing is more obvious than when units of m/s are used. This helps students to avoid using a diffusive conductance for water vapor when estimating a flux of carbon dioxide, which would result in a 60 percent error in the calculation. We have found that students adapt readily to the consistent use of molar units because of the simpler equations and explicit dependencies on environmental factors. The only disadvantage to using molar units is the temporary effort required by those familiar with other units to become familiar with " typical values " in molar units. A second convention in this book that is somewhat different from the first edition is the predominant use of conductance rather that resistance. Whether one uses resistance or conductance is a matter of preference, but predominant use of one throughout a book is desirable to avoid con - fusion. We chose conductance because it is directly proportional to flux, which aids in the development of an intuitive understanding of trans - port processes in complex systems such as plant canopies. This avoids some confusion, such as the common error of averaging leaf resistances to obtain a canopy resistance. Resistances are discussed and occasion - ally used, but generally to avoid unnecessarily complicated equations in special cases. A third convention that is different from the fist edition is the use of surface area instead of " projected area. " This first appears in the discussion of the leaf energy budget and the use of " view factors. " Because many bio - physicists work only with flat leaves, the energy exchange equations for leaves usually are expressed in terms of the " one - sided " leaf area; this is the usual way to characterize the area of flat objects. If the energy balance is generalized to nonflat objects, such as animal bodies or appendages, tree trunks or branches, or conifer needles, then this " one - side " area is subject to various interpretations and serious confusion can result. Errors of a factor of two frequently occur and the most experienced biophysi - cist has encountered difficulty at one time or another with this problem. We believe that using element surface area and radiation ''view factors " 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 develop- ment 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 one- half 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 Jkg 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, Jkg 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 contri- butions 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 teach- ing 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 [...]... from the absorption of acoustic energy from our surroundings Smell involves the flux of gases and aerosols to the olfactory sensors Numerous other sensations could be listed such as sunburn, heat stress, cold stress, and each involves the flux of something to or from the organism The steady-state exchange of most forms of matter and energy can be expressed between organisms and their surroundings as:... transport problems encountered by the design engineer These same models can be applied to transport processes between living organisms and their surroundings This book is written with two objectives inmind The first is to describe and model the physical microenvironment in which living organisms reside The second is to present simple models of energy and mass exchange between organisms and their microenvironmentwith... system or to a single component Clearly, one must define carefully what portion of the system is of interest in a particular analysis Animals may be components of this system from microscopic organisms in films of water in the soil to larger fauna such as worms, or animals onleaves such as mites or grasshoppers,or yet larger animals in the canopy space The particular microenvironmentthat the animal is... atmospheric thermal radiation view factor for dzfuse solar radiation view factor for ground thermal radiation view factor for solar beam xviii List of Symbols {mol m- 2 s- ' Ws2I {mol m- 2 s- ' {mol m- 2 s- I {mol mF2 s- I } } ) } {mol m- 2 s- I } {mol m- 2 s- I } {mol m- 2 s- ' {mol m- 2 s- ' {mol mF2 s- I {mol mP 2s- I {mol m- 2 s- I {w /m2 ) {m} ) ) } } } IJ SJ {w /m2 } {kg rnV 2s- ' ) {W m- ' c-I 1 { J/K} {m2 1s) {m2 IS}... etc A second heterogeneous natural system of interest to us is a plant canopy, which consists of leaves, branches, stems, h i t s , and flowers all displayed with elegance throughout some volume and able to move in response to wind, heliotropism, growth, or water stress Simple equations have beenused quite successfullyto describe light penetration and canopy photosynthesis by assuming the canopy to behave... two areas: use of mathematical models to quantify rates of energy and mass transfer and use of conservation principles to analyze mass and energy budgets of living organisms In quantification of energy and mass transfer rates, environmental biophysicists have followed the lead of classical physics and engineering There, theoretical and empirical models have been derived that can be applied to many of... flux density specific heat - Newton Pascal joule - watt - Symbol SI base units Derived Units m2 m3 m s- I kg m- 3 m kg s- 2 kg m- I s- 2 m2 kg s2 m2 s - ~ m2 kg s- 3 mol mol m- 2 s- I kg s3 m2 s- 2 K-I - N m- 2 Nm J kg-' J s- I - W m- 2 J kg-' K-' To make the numbers used with these units convenient, prefixes are attached indicating decimal multiples of the units Accepted prefixes, symbols, and multiples are shown... atmospheric pressure speciJic humidity (mass of water vapor divided by mass of moist air) PAR photonjux density xix List of Symbols {m2 s mol-' } {m2 s mol-' } {J mol-' C-' } {w /m2 ) {pmol m- 2 s- ' } {m4 s- I kg-' } {w /m2 ) {m4 s- ' kg-' ) heat transfer resistance (1/ g H ) vapor transfer resistance (1/g,) gas constant absorbed short- and long-wave radiation dark respiration rate of leaf resistance to waterflow... on spatial scale In environmental biophysics we consider natural materials such as soil, rock layers, vegetation mixtures, and animal coats The principles that are commonly used in environmental biophysics are most easily understood and used with pure materials Therefore a key aspect of environmental biophysics is knowing when assumptions of homogeneity are adequate, and when a meaningful solution to. .. exchanges The soil is obviously linked to the atmosphere by conduction and diffusion through pores, but it is also linked to the atmosphere through the plant vascular system Energy and mass conservation principles can be applied to this entire system or to specific componentssuch as a single plant, leaf, xylem vessel, or even a single cell The transport equations can also be applied to the entire system . {mol mF2 s- I } {mol m- 2 s- I } {mol m- 2 s- I } {mol m- 2 s- ' ) {mol m- 2 s- ' ) {mol mF2 s- I } {mol mP2 s- I } {mol m- 2 s- I } {w /m2 . reside. The second is to present a simplified discussion of heat - and mass - transfer models and apply them to exchange processes between organisms and