Wood Water Relations

Wood is formed in an essentially water-saturated environment in the living tree, and the cell wall remains in this state until the water flow from the roots is interrupted, such as by felling the tree. The wood then begins to lose most of its moisture by drying, resulting in changes in most of its physical properties. These changes, and their relationship to the environment to which the wood is subsequently ex posed, are the subject of this book. The text consists of six chapters. The first chapter discusses cer tain empirical relationships between wood and water, methods of measuring wood moisture content, factors which affect its equilib rium moisture content, and the effect of moisture content on wood strength. The second chapter treats the thermodynamics of moisture sorption by wood, inc1uding enthalpy, entropy, and free energy changes. The third chapter discusses some of the theories which have been proposed to explain the sorption isotherms for hygroscopic ma terials such as wood. Chapter 4 considers hygroexpansion or the shrinking and swelling of wood associated with moisture change. Chapter 5 is concerned with how moisture moves through the cell wall of wood in response to both moisture and temperature gradients. The sixth and final chapter discusses the theoretical and practical aspects of the electrical resistance and dielectric properties of wood, in c1uding the principles involved in their application in electrical moisture meters.

This book has a similar subject content to the author's previous Flow in Wood but with substantial updating due to the abundance of research in the wood science field since 1971. Several different concepts have been introduced, particularly in regard to wood-moisture relation ships. The role of water potential in the equilibria between wood and its humid and moist environments is considered. Two theories are introduced to explain the nonisothermal transport of bound water in the steady and unsteady states. As in the former text, the wood-. structure relationship is emphasized . . The author is especially grateful to Dr. C. Skaar for his careful and critical review of much of the manuscript and for the productive dis cussions of many of the concepts. Dr. T. E. Timell, the series editor, rendered major assistance in the preparation of Chap. 2 and in his editing of the manuscript. The author wishes to thank Dr. W. A. Cote, Mr. A. C. Day, and Mr. J. J. McKeon for providing electron micro graphs, Mr. G. A. Snyder for his photography of much of the art work, Dr. C. H. de Zeeuw for his advice in the field of wood anatomy, and Ms. Mary M. Siau for her careful rendition of the art work. Apprecia tion is extended to Miss Judy A. Barton and Mrs. Stephanie V. Micale for their work in typing and checking the manuscript. Mr. J. A.

This 15-chapter book is divided into four sections that discuss wood's structure and basic chemistry, its properties and reactivity, and its surface and degradation chemistry. The very basis of how wood is formed and the structure it assumes during this growth are given in the first section. Various wood science terms are defined and discussed thoroughly to give a clear and adequate foundation for the rest of the book. Wood water relationship important in almost any wood applications- are also discussed in this section. The subsequent three sections discuss relations and chemistry important for the beginning wood chemist to understand. These topics include wood's cell wall components, strength, interaction with preservatives, and adhesion. Wood polymer materials, wood surface activation, weathering and protection, and pyrolysis and fire retardancy are topics also embraced.

The first edition of this book was the first to provide an integrated description of sap ascension from an anatomical and functional point of view. The second edition opens with the three-dimensional aspects of wood anatomy. The cohesion-tension theory and new evidence are introduced in response to recent controversies over the mechanism of sap ascent in plants. The physiology, anatomy and biophysics of xylem dysfunction are discussed and new insights into hydraulic architecture are reviewed with special emphasis on physiological limits on maximum transpiration and how hydraulic architecture limits gas exchange, carbon gain and growth of plants. The text concludes with a description of xylem failure and pathology. The book highlights fascinating areas of current research with the aim to stimulate more work in the future.