190 



AMERICAN FORESTRY 



the piece. The volume of the piece is 

 the result. The sum of the volumes of 

 each piece gives the volume of the tree. 



However, in actual practice, it will 

 seldom be practicable or necessary to 

 make such a volume table. It will be 

 easier either to use the volume tables 

 already constructed, or to determine 

 the contents of average trees by actually 

 working them into the finished products, 

 and by measuring the amounts of those 

 products. 



The best volume tables give volumes 

 for trees not only of certain diameter 

 classes, but also for different heights 

 of each diameter class, because the 

 volume of trees varies, not only with 

 the difference in diameter, but also 

 largely with the difference in height. 

 That is, a tree of four inches in diameter 

 at breast height, that is twenty feet 

 high, will have a very much lower 

 volume than a tree four inches in 

 diameter and fifty feet high. 



It is then necessary in estimating, 

 either to record each tree separately as 

 to diameter and height, or to find the 

 average height of trees in each diameter 

 class. A simple way of determining 

 height is to place a ten-foot pole along- 

 side of the tree, and, stepping off to a 

 convenient distance from the tree, 

 figure the height by eye, comparing 

 the height of the tree with the ten-foot 

 pole. 



METHODS IN LARGE WOODLANDS. 



Where the area is too large to measure 

 all the trees, or where time does not 

 permit it, various short cuts to an esti- 

 mate may be used. 



One convenient way when the area 

 of the woodlot is known, is to measure 

 off some definite portion, such as one 

 acre or five acres, determine the amount 

 standing on this small area according 

 to the methods described before, and 

 multiply the amount on this area by 

 the figure which shows the proportion 

 between the small area, and the whole. 

 That is, if the small area is five acres, 

 and the whole one hundred acres, 

 multiply the volume on the small area 

 by twenty. 



Good judgment must be used in 

 order to select these sample plots that 



they shall be representative of the 

 whole area. It may be convenient to 

 know that a plot of 208 feet square 

 makes an acre; or that a circular plot 

 with a radius of 85 feet is a half acre. 



In still larger areas, where it is diffi- 

 cult to select sample plots which would 

 be fairly representative of the whole 

 stand, it is often convenient to run 

 strips at fixed intervals through the 

 stand. All the timber on these strips 

 is estimated and multiplied by the 

 number of times the strips are contained 

 in the total area. Strips should always 

 be run at right angles to the main 

 slopes; that is, up and down hills, rather 

 than alomg them. Where very noted 

 changes in the type of forest occur, the 

 amounts in each type on the strips 

 should be estimated separately, and 

 the estimate applied to the area of each 

 type. 



It will be seen from this that in using 

 these methods it is necessary to know 

 at least the total area of woodland, and 

 it is much better also to know the area 

 of each type. This involves the map- 

 ping of the area. 



It is not possible to describe here the 

 way to make such forest maps. Unless 

 the area is very large, or a very accurate 

 map is wanted, a fairly good map may 

 be made by the use of an ordinary hand 

 compass, and by pacing, or else by 

 chaining distances. 



In estimating strips, it is most con- 

 venient either to take 16^ feet on each 

 side of the line run, or 33 feet on each 

 side. Then, for every chain (66 feet) 

 forward along the strip, in case where 

 16^2 feet on each side of the line has 

 been taken, one-twentieth of an acre 

 has been estimated; where 33 feet on 

 each side of the line, one-tenth of an 

 acre; for every tally of 10 chains (66 

 feet) in the wider strip, an acre has been 

 estimated; in the smaller, one-half acre. 



It is best to tally each acre separately ; 

 and where the line ends before a whole 

 acre has been estimated, the number of 

 chains should be noted, and that frac- 

 tion of an acre used for the strip esti- 

 mated, rather than continuing on the 

 same sheet back on another line. 



Strips sixty-six feet wide, run one- 

 quarter mile apart, will give an estimate 



