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A VOLUME TABLE FOR RED MAPLE ON THE

HARVARD FOREST

E. E. CARTER

ASSISTANT PROFESSOR OF FORESTRY

RED MAPLE (Acer rubrum) is the most important of the trees cut for cordwood on the Harvard Forest. More than half of the total cut of fuel wood, and more than seventy-five per cent of the " hardwood" is of this species. Of the trees used primarily for fuel, only gray birch (Betula populifolia) approaches it in numbers in the Forest, and the small size of the birch makes insignificant its proportion of the total volume cut.

The maple is present on nearly every wooded acre within the Forest. The heaviest stands are in the hollows or swales where the ground is moist, but not swampy. On such situations small stands of nearly pure red maple may be found, with only a scattering mixture of other species such as white elm (Ulmus americana), chestnut (Castanea dentata), black cherry (Prunus serotina), white ash (Fraximus americana), and yellow birch (Betula lutea). Here the tree reaches its best development for cordwood, the usually dense stand forcing height growth to an extent that produces trees eighty to ninety feet tall, and with few large limbs. Stands of forty to fifty cords per acre are not uncommon.

In the swamps, maple occurs in mixture with red spruce (Picea rubens), hemlock (Tsuga canadensis), tamarack (Larix laricina), and tupelo (Nyssa sylvatica). On such situations the maple has a relatively poor form, caused by the poor soil and the bad treatment of the forest in the past. The trees are short, often unsound, and usually very limby or forked. As a rule the stand of cordwood is not heavy. The same poor form is found in some swales where past logging opened the stand and caused the development of heavy crowns with forked and branchy stems.

On the slopes and ridges maple, although practically always present, is a much less important member of the tree community. Here white pine (Pinus strobus) is the most abundant species,

although on some slopes chestnut, red oak (Quercus rubra), and other broadleaf species form the stand. In either case, the maple is numerically unimportant, usually occurs as single trees, and is usually removed in thinning, that the saw-timber species may be benefited. Only on those slopes and ridges which were cut clean twenty years ago is the maple considered to be a valuable species and there only because it is a better tree than the gray birch, which occupies most of the ground.

The low price of red maple boards, the frequence of the defect known as "black heart" and the heavy weight of the logs and lumber make it unusual for even a good sized tree of this species to yield saw logs which can be handled at a profit in this region. In estimating, maple of any size not too large to be split without powder is usually classed as cordwood. On the Harvard Forest, red maples larger than fifteen inches D B H are infrequent, and up to that size the choppers have little difficulty in splitting the butt cuts with wedges.

The importance of the species in the operation of the Forest led to the collection by the classes of 1912 and 1913, Harvard Forest School, of the data here presented. Most of the trees were cut by the students, but some were measured after being felled by the wood-choppers. The measurements taken on each tree were the D B H, the total height, and the mid DO B of each length of merchantable cordwood, stem and limb wood being recorded separately. The crown class of each tree, and the type in which it stood were also recorded. The number of trees measured is insufficient to give reliable results when considered for the relations of volume to crown class, or type, or for the relation of limb wood to stem wood. It is hoped to develop these relations through additional data.

Every care was taken to make the measurements represent the utilization customary in the vicinity. As a rule, bolts larger than eight inches in diameter were measured exactly four feet in length, since sticks larger than this diameter are ordinarily cut with a saw. Bolts smaller than eight inches were allowed a length of 4.2 feet, since they are usually cut with an axe, but were cubed as four foot sticks. Limbs and tops were considered merchantable whenever a four foot stick with a mid D O B of two inches or more could be

TABLE I

TABULATION OF DATA FOR VOLUME TABLE FOR RED

MAPLE

Based on Measurements taken in 1910 and 1911 in Harvard Forest,
Petersham, Mass.

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This class includes all trees 35.1 feet to 45.0 feet in height, and therefore some trees below 7 inches DBH which were also used in computing the averages for the 35 foot class. The averages for the trees 37.6 feet to 45.0 feet in height were as follows:

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secured, but here again the usual tendency of choppers to disregard possible lengths from the limbs of large trees and to use tops and limbs of small trees to somewhat less than two inches was followed.

As may be inferred from the wide range of heights for each diameter below fourteen inches (see Table I), measurements were taken in many places and in a wide variety of types, including bottom or swale, pine slope, swamp, and birch and maple coppice. Most of the trees more than six inches DBH were of seedling origin.

The volume of each tree was determined by computing the volume of each bolt by Huber's formula (BL) and then adding the volumes of the several bolts. The volumes of trees with the same D B H and height were then averaged. These computations were checked, and partially rechecked. The averages were then tabulated with the number of trees averaged indicated by a small figure below and to the right of the figure for the volume, and when there was but one tree, the diameter shown by small figures above and to the left. Thus 13.168, indicates that there was one tree of a certain diameter class and height class, the exact diameter being 10.1 inches and the volume 13.168 cubic feet.

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The irregularities in the foregoing table are numerous, especially in the higher diameters in which few trees were secured. remove these irregularities the data was plotted on cross section paper, and a curve drawn for each height class showing the volumes. of trees of different diameters within that height class. In entering the data, the notation of the actual diameter of the single trees which were secured for some diameters enabled accurate plotting to be done, and the number of trees averaged to give the volumes was entered in each case so that due weight could be given in drawing the curves. The results showed some irregularities still present, especially in the seventy foot height class. The corrected data were again plotted so that a curve could be drawn for each diameter class showing the volumes of trees of different heights, and the readings from these curves were again plotted and a new curve for each height class drawn, superseding the first set of curves. The resulting readings are given in Table II.

The volumes for trees in the two inch D B H class are so small, and the habits of wood choppers in cutting up such small trees

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