CANADIAN FORESTRY ASSOCIATION 41 



Some multiply the estimated number of trees by the contents of the average tree, 

 making due allowance for defects; others count the trees and multiply by the 

 estimated contents of average trees, allowing for defects; and still others estimate 

 the contents of each tree separately, making deductions for unsoundness and other 

 imperfections. In the case of irregular hardwood stands, this latter is the only 

 method of estimating, because many of the older trees are almost worthless for 

 saw timber, and would not pay for the cost of removing them. 



The more defective the trees are, the more preferable is the judgment of esti- 

 mators who have had long experience in the mill and in the woods, to the methods 

 of mere measuring. In sound timber, however, the method of measuring the 

 trees on a known percentage of the total area is much preferable to the ocular esti- 

 mate of a timber cruiser no matter how experienced. Furthermore, a cruiser 

 may be able to estimate pretty closely in the locality in which he has had long 

 experience, and in a new region finds himself very much "at sea". Possibly this 

 fact explains the origin of theterm "cruiser." Be that as it may, the cruiser finds 

 it necessary to establish a new standard which will enable him to estimate correctly 

 the contents of stands in the new region in which he finds himself. The quickest 

 and surest way to establish such a standard is by a careful selection and exact meas- 

 urement of representative trees in the stand. Having established his new standard 

 of reference he is then in a position to correctly estimate the volume of the timber 

 in the new locality in which he finds himself. When the timber is fairly uniform 

 in size and evenly distributed over the tract it may suffice to estimate the yield of 

 a few sample acres, find their average and multiply by thetotal acreage. Usually, 

 however, the timber is not uniform, and it is necessary to estimate the lower slopes 

 of a mountain separately from the upper, the north slope separately from the 

 south, and the water-sheds, swamps and other special types, separately also. To 

 meet this difficulty, the plan of estimating the timber on sample areas aggregating 

 a given percentage of the whole tract has been devised. If properly distributed 

 they give a very close average for the timber on the tract. 



SAMPLE PLOT METHODS. 



Many methods have been devised for the proper location and rapid laying out 

 of sample plots. Usually they are laid out in the form of circles, squares or rec- 

 tangular strips, and in area generally vary from one-quarter of an acre to a whole 

 acre. A quarter acre circle has a radius of 19.62 yards, and an acre circle a 

 radius of 39.24 yards. In the form of a square each edge of the acre is 69.57 

 yardst and of the quarter acre 34.78 yards. 



In open stands of timber one of the quick methods is to travel in parallel 

 lines a quarter of a mile apart and stop every quarter of a mile to lay out an acre 

 (with a radius of 39 yards or a side of 69 yards) and estimate the timber upon it. 

 This would give us sixteen sample acres equally spaced over each square mile and 

 therefore represent one-fortieth, or 2$%, of its area. With a little practice the 

 estimator soon learns to judge whether a tree is within thirty-nine yards or not 

 of the centre of the circle where he stands. Another plan is to place a flag at the 

 centre and walk through the timber within thirty-nine yards of it, making the 

 estimate by eye, by counting trees, or by measuring. Returning to the flag he 

 can then pick up his compass direction, pace a quarter of a mile, and estimate the 

 next acre. In dense stands it is not easy to see all trees within thirty-nine yards, 

 and it is preferable to use either half-acre or quarter-acre circles instead, with radii 

 of 24.75 yards and 19.62 yards, respectively. For ruogh estimating it is custom- 



