Part 1 (1/2)
American Forest Trees.
by Henry H. Gibson.
PREFACE
The material on which this volume is based, appeared in Hardwood Record, Chicago, in a series of articles beginning in 1905 and ending in 1913, and descriptive of the forest trees of this country. More than one hundred leading species were included in the series. They const.i.tute the princ.i.p.al sources of lumber for the United States. The present volume includes all the species described in the series of articles, with a large number of less important trees added. Every region of the country is represented; no valuable tree is omitted, and the lists and descriptions are as complete as they can be made in the limited s.p.a.ce of a single volume. The purpose held steadily in view has been to make the work practical, simple, plain, and to the point. Trees as they grow in the forest, and wood as it appears at the mill and factory, are described and discussed. Photographs and drawings of trunk and foliage are made to tell as much of the story as possible. The pictures used as ill.u.s.trations are nearly all from photographs made specially for that purpose. They are a valuable contribution to tree knowledge, because they show forest forms and conditions, and are as true to nature as the camera can make them. Statistics are not given a place in these pages, for it is no part of the plan to show the product and the output of the country's mills and forests, but rather to describe the source of those products, the trees themselves. However, suggestions for utilization are offered, and the fitness of the various woods for many uses is particularly indicated. The prominent physical properties are described in language as free as possible from technical terms, and yet with painstaking accuracy and clearness. Descriptions intended to aid in identification of trees are given; but simplicity and clearness are held constantly in view, and brevity is carefully studied. The different names of commercial trees in the various localities where they are known, either as standing timber or as lumber in the yard and factory, are included in the descriptions as an a.s.sistance in identification. The natural range of the forest trees, and the regions where they abound in commercial quant.i.ties, are outlined according to the latest and best authorities. Estimates of present and future supply are offered, where such exist that seem to be authoritative. The trees are given the common and the botanical names recognized as official by the United States Forest Service. This lessens misunderstanding and confusion in the discussion of species whose common names are not the same in different regions, and whose botanical names are not agreed upon among scientific men who mention or describe them. The forests of the United States contain more than five hundred kinds of trees, ranging in size from the California sequoias, which attain diameters of twenty feet or more and heights exceeding two hundred, down to indefinite but very small dimensions. The separating line between trees and shrubs is not determined by size alone. In a general way, shrubs may be considered smaller than trees, but a seedling tree, no matter how small, is not properly called a shrub. It is customary, not only among botanists, but also among persons who do not usually recognize exact scientific terms and distinctions, to apply the name tree to all woody plants which produce naturally in their native habitat one main, erect stem, bearing a definite crown, no matter what size they may attain.
The commercial timbers of this country are divided into two cla.s.ses, hardwoods and softwoods. The division is for convenience, and is sanctioned by custom, but it is not based on the actual hardness and softness of the different woods. The division has, however, a scientific basis founded on the mechanical structures of the two cla.s.ses of woods, and there is little disagreement among either those who use forest products or manufacture them, or those who investigate the actual structure of the woods themselves, as to which belong in the hardwood and which in the softwood cla.s.s.
_Softwoods_--The needleleaf species, represented by pines, hemlocks, firs, cedars, cypresses, spruces, larches, sequoias, and yews, are softwoods. The cla.s.sification of evergreens as softwoods is erroneous, because all softwoods are not evergreen, and all evergreens are not softwoods. Larches and the southern cypress shed their leaves yearly.
Most other softwoods drop only a portion of their foliage each season, and enough is always on the branches to make them evergreen. Softwoods are commonly called conebearers, and that description fits most of them, but the cedars and yews produce fruit resembling berries rather than cones. Though the needleleaf species are cla.s.sed as softwoods, there is much variation in the absolute hardness of the wood produced by different species. The white pines are soft, the yews hard, and the other species range between. If there were no other means of separating trees into cla.s.ses than tests of actual hardness of wood, the line dividing hardwoods from softwoods might be quite different from that now so universally recognized in this country.
_Hardwoods_--The broadleaf trees are hardwoods. Most, but not all, shed their foliage yearly. It is, therefore, incorrect to cla.s.sify deciduous trees as hardwoods, since it is not true in all cases, any more than it is true that softwoods are evergreen. Live oaks and American holly are evergreen, and yet are true hardwoods. In a test of hardness they stand near the top of the list.
There are more species of hardwoods than of softwoods in this country; but the actual quant.i.ty of softwood timber in the forests greatly exceeds the hardwoods. Nearly two hundred species of the latter are seldom or never seen in a sawmill, while softwoods are generally cut and used wherever found in accessible situations.
As in the case of needleleaf trees, there is much variation in actual hardness of the wood of different broadleaf species. Some which are cla.s.sed as hardwoods are softer than some in the softwood list. It is apparent, therefore, that the terms hardwood and softwood are commercial rather than scientific.
Palm, cactus, and other trees of that cla.s.s are not often employed as lumber, and it is not customary to speak of them as either hardwoods or softwoods.
_Sapwood and Heartwood_--Practically all mature trees contain two qualities of wood known as sap and heart. The inner portion is the heartwood, the outer the sap. They are usually distinguished by differences of color.
The terms are much used in lumber transactions and are well understood by the trade. The two kinds of wood need be described only in the most general way, and for the guidance and information of those who are not familiar with them. Differences are many and radical in the relative size and appearance of the two kinds of wood in different species, and even between different trees of the same species. No general law is followed, except that the heartwood forms in the interior of the tree, and the sapwood in a band outside, next to the bark. In the majority of cases young trees have little heartwood, often none. It is a development attendant on age, yet age does not always produce it. Some mature trees have no heartwood, others very little.
The two kinds of wood belong to needleleaf and broadleaf trees alike; but palms, owing to their manner of growth, have neither. Their size increases in height rather than in diameter. With palms, the oldest wood is in the base of the trunk, the newest in the top; but in the ordinary timber tree the oldest wood is in the center of the trunk, the youngest in the outside layers next the bark. It is the oldest that becomes heartwood, and it is, of course, in the center of the tree. The band of sapwood is of no certain thickness, but averages much thicker in some species than in others. The sapwood of Osage orange is scarcely half an inch thick, and in loblolly pine it may be six inches or more.
Heartwood is known by its color. The eye can detect no other difference between it and the surrounding band of sapwood. There is no fundamental difference. The heart was once sapwood, and the latter will sometime become heartwood if the tree lives long enough. As the trunk increases in size and years, the wood near the heart dies. It no longer has much to do with the life of the tree, except that it helps support the weight of the trunk. The heartwood is, therefore, deadwood. The activities of tree life are no longer present. The color changes, because mineral and chemical substances are deposited in the wood and fill many of the cavities. That process begins at the center of the trunk and works outward year by year, forming a pretty distinct line between the living sapwood and the dead and inert heartwood.
For some reason, the heartwood of certain species is p.r.o.ne to decay.
Sycamore is the best example. The largest trunks are generally hollow.
The heart has disappeared, leaving only the thin sh.e.l.l of sapwood, and this is required not only to maintain the tree's life and activities, but to support the trunk's weight. In most instances the substances deposited in the heartwood, and a.s.sociated with the coloring matter, tend to preserve the wood from decay. For that reason heart timber lasts longer than sap when exposed in damp situations. The dark and variegated shades of the heartwood of some species give them their chief value as cabinet and furniture material. The sapwood of black walnut is not wanted by anybody, for it is light in color and is characterless; but when the sap has changed to heart, and its tones have been deepened by the acc.u.mulation of pigments, it becomes a choice material for certain purposes. The same is true of many other timbers, notably sweet and yellow birch, black cherry, and several of the oaks.
It sometimes happens that when sapwood is transformed into heart, a physical change, as well as a coloring process, affects it. Persimmon and dogwood are examples, and hickory in a less degree. The sapwood of persimmon and dogwood makes shuttles and golf heads, but after the change to heartwood occurs, it is considered unsuitable. Handle makers and the manufacturers of buggy spokes prefer hickory sapwood, but use the red heartwood if it is the same weight as the sap.
_Annual Rings_--The trunks of both hardwoods and softwoods are made up of concentric rings. In most instances the eye easily detects them. They are more distinct in a freshly cut trunk than in weathered wood, though in a few instances weathering accentuates rather than obliterates them.
A count of the rings gives the tree's age in years, each ring being the growth of one year. An occasional exception should be noted, as when accident checks the tree's growth in the middle of the season, and the growth is later resumed. In that case, it may develop two rings in one year. A severe frost late in spring after leaves have started may produce that result; or defoliation by caterpillars in early summer may do it. Perhaps not one tree in a thousand has that experience in the course of its whole life. Trees in the tropics where seasons are nearly the same the year through, seldom have rings. Imitations of mahogany are sometimes detected by noting clearly marked annual rings. It is difficult for the woodfinisher to obliterate the annual rings, but some of the French woodworkers very nearly accomplish it.
No law of growth governs the width of yearly rings, but circ.u.mstances have much to do with it. When the tree's increase in size is rapid, rings are broad. An uncrowded tree in good soil and climate grows much faster than if circ.u.mstances are adverse. Carolina poplar and black willow sometimes have rings nearly three-fourths of an inch broad, while in the white bark pine, which grows above the snow line in California, the rings may be so narrow as to be invisible to the naked eye.
There is no average width of yearly rings and no average age of trees. A few (very few) of the sequoias, or ”big trees” of California, are two thousand years old. An age of six or seven centuries appears to be about the limit of the oldest of the other species in this country, though an authentic statement to that effect cannot be made. There are species whose life average scarcely exceeds that of men. The aspen generally falls before it is eighty; and fire cherry scarcely averages half of that. Of all the trees cut for lumber, perhaps not one in a hundred has pa.s.sed the three century mark. That ratio would not hold if applied to the Pacific coast alone.
_Spring and Summerwood_--These are not usual terms with lumbermen and woodworkers, but belong more to the engineer who thinks of physical properties of timber, particularly its strength. Yet, sawmill and factory men are well acquainted with the two kinds of wood, but they are likely to apply the term ”grain” to the combination of the two.
Spring and summerwood make the annual ring. Springwood grows early in the season, summerwood later. In fact, it usually is the contrast in color where the summerwood of one season abuts against the springwood of the next which makes the ring visible. The inside of the ring--that portion nearest the heart of the tree--is the springwood, the rest of the ring is the summerwood. The former is generally lighter in color.
Sometimes, and with certain species, the springwood is much broader than the other. The summerwood may be a very narrow band, not much wider than a fine pencil mark, but its deeper color makes it quite distinct in most instances. In other instances, as with some of the oaks, the summerwood is the wider part of the annual ring. The figure or ”grain” of southern yellow pine is largely due to the contrast between the dark summerwood and light springwood of the rings. The same is true of ash, chestnut, and of many other woods.
_Pores_--Wood is not the solid substance it seems to be when seen in the ma.s.s. If magnified it appears filled with cavities, not unlike a piece of coral or honeycomb; but to the unaided eye only a few of the largest openings are visible, and in some woods like maple, none can be seen.
The large openings are known as pores. They are so prominent in some of the oaks that in a clean cut end or cross section they look like pin holes. Very little magnifying is required to bring them out distinctly.
A good reading gla.s.s is sufficient.