A Thesis Presented To The faculty Of The Graduate School At Cornell University For The Degree
Of Master In Forestry
By Albert Abraham Kraus. B. S.
1918
A Hemlock Bark Study In Culled Forests Of The Western Adirondacks.
With the rise in prices of hemlock and bark, the hemlock has become of such importance that it was decided at a seminar held early in August to include in the forthcoming working plan supplement for the Cutting Game Preserve a complete estimate of the amount of hemlock bark present on the remaining sections of the tract.
The stands are on. the Cutting Game Preserve in St. Lawrence Co., W. Y,, in the northwestern part of the Adirondacks. In 1898, 19 years ago, the tract was cut over for the softwoods--hemlock , spruce, white pine, and balsam--the best of which were taken down to a diameter limit of about 12 inches. This left a culled forest, the present stand. The hemlocks left were either small or defective, but still in a good enough condition to respond to the greater amount of light admitted by the cuttings.
To furnish such an estimate there must be:--
first: a stand table giving the number of size classes and the total number of trees in each size class area under question. Those data will be obtained from the field notes of the strip survey which the seniors are running.
second: tables giving the average amount of bark obtainable under the given conditions from a tree of each size class.
The construction of such a table is one of the purposes of the field and office work in connection with this report. The required estimate (total volume of bark) is then obtained by multiplying the total number of trees in each size class by the average amount of bark of a tree of that size class, and then totaling the figures. At present (Aug. 1917) there is conducted, on a part of this preserve, a logging operation in which hemlock is being cut and the bark stacked. The stands here are the same kind as those for which the estimate is to be made.
Since the operation is in practically the same kind of a stand and conducted by the same man, there is unusual opportunity for the construction of local volume tables and gathering data regarding the costs and the methods used.
How hemlock bark is gathered.
Bark peeling must be done during the season when the bark comes off easily. The season in these parts begins early in May and ends late in August. The actual work of felling the trees and peeling was begun late in July and carried on until the end of August. Three men made up a crew -- two felling and one swamping and peeling. The number of trees that a man can peel per day is given in table below. After the tree is felled the man lays off (on the bole), four foot lengths with his axe handle, and cuts around the tree at those points. He then makes a longitudinal slit along the top of the bole and strips the bark off with a spud. "Spud" is the trade name for the tool used to sever the bark from the tree. The bark is then piled near the tree, care being taken to keep the cambium side down, so that the tannin will not leach out. The timber is not cut into logs at this time, but this is deferred until early in September when bucking-up and skidding begin. The bark is then hauled on bark drays and hauled to the main hauling roads where it is stacked into "ricks". A picture of a dray and a rick is included at the end of the report. These ricks remain here until the hauling season which begins as soon as there is sufficient snow on the ground to form a good road surface when the bark is hauled in sleds to cars and loaded.
All logs, whether hemlock, spruce, or balsam, are peeled in the woods. Since the bark is left in the woods, the weight of the logs is reduced and the freight cost lowered. At the same time the loss of wood in barking with the rossing machines at the mill is eliminated. It is there fore real economy, in the case of railroad transportation jobs, to peel the logs in the woods and this peeling cost should be charged against the logs and not against the bark which is a by-product.
A man can peel from forty to fifty trees per day, depending on the efficiency of the labor. Below is a foreman's record of a days work.
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Aside from showing the number of trees a man can peel per day, the figures are interesting because they show the greater efficieincy of the American and Indian labor over the Polacks on the job.
In figuring the cost of producing the bark, the cost of transportation is the main item. A bark dray drawn by one horse and tended by one man makes about fifteen trips a day, with an average distance of 800 feet per trip, carrying one-half cord of the bark each time from where it has been piled near the tree to the hauling road. The remainder of the trip, from the rick to the railroad, is done by a driver and one team which can haul about five cords a day.
Cost fro tree to rick: 1 man- $2.00 for wages and $1.00 for keep-------$3.00
1 horse - $1.00 for keep and $1.00 for hire----$2.00
Cost from rick to rail: 1 man--$3.00
2 horses--4.00
Total per day--$7.00
Per cord---from tree to rick-$0.72
from rick to rail-$1.40
Total-$2.12
The best quality of bark is usually obtained from the larger trees and comes in large thick slabs, free from holes and with the least tendency to curl in drying. Thin bark is not taken because it brings a lower price and is hard to handle. The thinner the bark the more it curls and breaks in drying. Since bark is sold by weight there is a minimum thickness which it does not pay, because the market price of a slab will be less than the cost of production.
A minimum thickness of one-hilf inch at the upper end is used in this job, and the bark is taken from the bole up to a point where this thickness is reached. The tables which follow are based on this standard of utilization.
Factors determining the amount of bark in a forest.
The factors entering into the determination of the amount of bark which will be obtained from a logging area may be divided into two main groups-- (a)the natural factors or those determining the total amount of bark on the area, and (b) the utilization factors, those determining the amount taken.
Under natural factors are included the character of the stand, its location, previous history; the character of the trees, their diameter, height, and form; the thickness of the bark.
The stand has been described in a previous part of this report. Individual trees yield different amounts of bark. Under normal conditions the volume of bark increases with the increase in diameter and height. For example, a 12 inch ( at diameter breast high ) hemlock has a bark thickness of about three-fourths inch, while in a 16-inch tree the bark is about an inch thick. (See table at the end of report.) The height to which the tree has cleared itself of limbs is a factor since bark is usually not taken above the clear length because of the holes left by the branches.
Ex, A 16 inch well formed tree yielded 15.7 cubic feet of bark while a 17 inch tree with a large branch coming off at thirty feet from the ground yielded 10 cubic feet. A rapidly tapering tree will yield less bark than one that approaches a more cylindrical form since naturally the circumference Bit the top would be greater in the latter case yielding broader pieces.
The utilization factors deal with the way the work is done and the character of the labor. The various crews have different ideas regarding the peeling and the amount of bark to obtain from a tree. Differences from 10% to 40% in volume of bark obtained were noted for similar sized trees. The men estimate by eye where the bark becomes too thin to be taken, some going lower than others. This introduces one ground for difference.
On large-trees all the bark on the underside can not be readily obtained. This ie because the trees are so large that the man can not roll them over. On such trees a lot of bark is usually left but some crews take more than others. £x. A 29 inch tree in which there was complete utilization, due to the fact that it was so lodged that the men could readily get to the underside, yielded 70.4 cubic feet of bark, while a 27 inch tree in which the bark was taken on the upper side only yielded but 36 cubic feet. Other differences due to negligence on the part of the men were noted.
The field work.
The field work consisted in noting the following data for every hemlock from which the bark could clearly be distinguished .
1. Number of the tree. Each tree was assigned a number for future identification in case rechecking was necessary
. 2. Diameter breast high. See under office work.
3. Stump height. In each case the stump height was measured to the nearest inch.
4. Stump diameter outside the bark to tenths of inches. '
5. Stump diameter inside bark. Inches and tenths.
6. Total height of the tree. The reason for taking the total height was to see if there was any relation between the volume and the D. B. H. on various heights.
7. The height above the stump to which the bark had been taken.
8. The diameter at that point. See 7.
9. The volume of bark, obtained by measuring the dimensions of the pile with a two foot rule, allowing enough in each case to reduce the volume to that which it would occupy if compacted under pressure.
10. Remarks, Under remarks come such notes as the form of the tree, degree of utilization; rapidity of taper.
In many cases these were very important since they explain apparent discrepancies. For example, one tree, (#229) a 15 inch hemlock, yielded 7.8 cubic feet of bark while another 15 inch hemlock gave 16.0 cubic feet. The remarks explain that the difference is due to the fact that the utilization is much closer in the second case. Another example is in the case of trees #513 and 519, both 34 inch trees. The first gave a yield of 72 cubic feet and the second of 54 cubic feet, the difference being due to the degree of utilization..
The office work consisted in working up the diameter breast high from the stump height and taper curves which had been prepared two years previously in connection with the working plan made by the graduates at the time. The volumes and diameters were then plotted on cross section paper and an harmonized curve drawn. This curve shows the average yield per tree under the present conditions.
The main results of the work are the curves at the end of this report and the following tables read from the curves. In the last two columns are figures from other tables for comparison.
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It is interesting to note that Mr. Cutting, the owner, estimates that he will get a cord of bark from every four tree between 18 inches and 24 inches in diameter, which compares well with the curve.
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Conclusions. Comparisons of the bark volume and thickness of bark with values from other tables show no great difference. This may be because the tables were made in sands of the same nature or that the volume and thickness of the bark is nearly constant for each diameter regardless of site conditions and method of treatment.
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