Forest Products and Wood Science

An Introduction

Rubin Shmulsky, P. David Jones

• Editorial: Wiley-Blackwell
• Año: 2018
• ISBN:
  9781119426370
• Edición: 7
• Categoría: Biowissenschaften
• Categoría: Botanik

The updated seventh edition of the classic text on wood science and forestry

The seventh edition of Forest Products and Wood Science: An Introduction offers a fully revised and updated review of the forest products industry. This classic text contains a comprehensive review of the subject and presents a thorough understanding of the anatomical and physical nature of wood. The authors emphasize its use as an industrial raw material.

Forest Products and Wood Science provides thorough coverage of all aspects of wood science and industry, ranging from tree growth and wood anatomy to a variety of economically important wood products, along with their applications and performance. The text explores global raw materials, the increasing use of wood as a source of energy and chemicals and environmental implications of the use of wood. This edition features new material on structural composites, non-structural composites, durability and protection, pulp and paper, energy and chemicals, and global raw materials. This seventh edition of the classic work:

• Contains new information on a variety of topics including: structural composites, non-structural composites, durability and protection, pulp and paper, energy and chemicals and global raw materials
• Includes a fully revised text that meets the changing needs of the forestry, engineering, and wood science academics and professionals
• Presents material written by authors with broad experience in both the private and academic sectors

Written for undergraduate students in forestry, natural resources, engineering, and wood science, as well as forest industry personnel, engineers, wood-based manufacturing and using professionals, the seventh edition of Forest Products and Wood Science updates the classic text that has become an indispensable resource.

CHAPTER 1
Tree Growth and Production of Woody Tissue

Trees are complex organisms. Originating through vegetative propagation or from sexually fertilized eggs that become tiny seed‐encased embryos, trees grow to be one of nature's largest living organisms.

Like humans, trees are delicate when young and typically grow vigorously when given proper nutrition and a suitable environment. As juveniles, they form tissues that differ from those in mature trees. They respire. They require a balanced intake of minerals to maintain health. They metabolize food, but unlike humans they also synthesize their own foods. If wounded, they react quickly to effect healing. As age progresses, vigor is maintained for a lengthy period but then begins to wane. Life processes eventually slow to the point that the tree has difficulty healing wounds and warding off disease. Finally, the tree dies.

The focus of this book is not on the growth process but on an important product of growth: wood. However, a brief study of the process of wood formation provides a useful basis for a study of wood itself.

Wood is formed by a variety of plants, including many that do not attain tree stature. A tree is generally defined as a woody plant 4–6 m (15–20 ft) or more in height and characterized by a single trunk rather than several stems. Plants of smaller size are called shrubs or bushes. Species that normally grow to tree size may occasionally develop as shrubs, especially where growth conditions are adverse. Because of the size attained, wood produced by plants of tree stature is useful for a wider range of products than wood from shrubs and bushes. For this reason, wood produced by trees is emphasized.

Classification of Woody Plants

Woods, and the trees that produce them, are divided into two categories: hardwoods and softwoods. Hardwood and softwood trees are botanically quite different. Both are included in the botanical division spermatophytes (Table 1.1), meaning that they produce seeds. They are, however, in different botanical subdivisions. Hardwoods are in the subdivision angiospermae and softwoods are in the gymnospermae subdivision. Angiosperms are characterized by the production of seeds within ovaries, whereas gymnosperms produce seeds that lack a covering layer.

TABLE 1.1. Trees in the plant kingdom.

Divisions:	Thallophytes	Bryophytes	Pteridophytes	Spermatophytes (seed plants)
	Algae	Mosses	Ferns
	Fungi	Liverworts	Horsetails
			Rushes
Subdivisions:		Gymnosperms	Angiosperms
		(naked seed)	(seed in fruit)
Orders:	Cycadales	Ginkgoales	Gnetales	Coniferales
Classes:	Monocots	Dicots		Yucca
	(palm‐like)	(rare)
Families:	Cupressaceae	Taxaceae	Pinaceae	Taxodiaceae
	Cedar	Yew	Fir	Redwood
	Juniper	Larch	Hemlock	Baldcypress
	Cypress		Pine
			Spruce

25 families in the United States.

Needle‐like leaves characterize softwood trees. Such trees are commonly known as evergreens, because most remain green the year around, annually losing only a portion of their needles. Most softwoods also bear scaly cones (inside which seeds are produced) and are therefore often referred to as conifers. Included in the softwood group in the Northern Hemisphere are the genera Pinus (pine), Picea (spruce), Larix (larch), Abies (fir), Tsuga (hemlock), Sequoia (redwood), Taxus (yew), Taxodium (cypress), Pseudotsuga (Douglas‐fir), and the genera of those woods known commonly as cedars (Juniperus, Thuja, Chamaecyparis, and Calocedrus).

In contrast to softwoods, hardwoods are angiosperms that bear broad leaves (which generally change color and drop in the autumn in temperate zones) and produce seeds within acorns, pods, or other fruiting bodies. Referring again to Table 1.1, note that angiosperms are subdivided into monocotyledons and dicotyledons. Hardwood‐producing species fall within the dicotyledon class. Hardwood genera of the Northern Hemisphere include Quercus (oak), Fraxinus (ash), Ulmus (elm), Acer (maple), Betula (birch), Fagus (beech), Populus (cottonwood, aspen) and others. Included in the monocotyledon class are the palms and yuccas. Many of the roughly 2500 species of palms produce relatively large‐diameter fibrous stems, which are strong if left in the round condition but tend to fall apart when cut into lumber; some species of palm, however, produce stems suitable for the production of local‐use construction “lumber.” Composite panels and flooring can be made from partially refined stems and paper can be made from the fiber.

Not only do hardwood and softwood trees differ in e...