PERIODICAL LITERATURE 487 



ning very extensively, and discussions on results of various degrees of 

 thinning have also been rare. 



The data were secured from a stand of 50 to 60 year-old fir on two 

 sample plots first, to which, sixteen years later, a third one was added. 

 Plots A and B were thinned in 1886 and 1899, but to secure data indi- 

 cating an optimum at least a third plot needed to be thinned to a 

 different degree, and this was done in 1902.' At that time, and again in 

 1911, the measurements from all three plots, with proper allowances 

 for the added plot, were secured and tabulated for easy comparison. 

 The thinnings in 1902 removed 29, 25 and 23 per cent of volume, 

 respectively, from the three plots. A, B and C. Before the 1902 thin- 

 ning there were in A much fewer (20 per cent less) trees than in B, 

 but a slightly larger volume and circumference (diameter) of average 

 tree. Owing to the deficiency in tree numbers, however, both basal 

 area and total volume were smaller than in B. The 29 per cent thin- 

 ning in A removes a larger number of trees, yet a smaller absolute 

 volume than the 25 per cent thinning in B, and also leaves a smaller 

 total volume; but the volume of the average tree in A is increased (by 

 the removal of so many inferior trees). 



The changes in nine years following the 1902 thinning show the 

 circumference of the average tree in A to have increased by only 3 

 centimeters and in B by 5 centimeters, but the volume of the average 

 tree has increased .093 cm. in A as against only .063 cm. in B ; yet the 

 total basal area, which was smaller before in A, has remained so, 

 although its increment is slightly larger than in B. 



The absolute volume and value production in A has, however, 

 remained behind; on the contrary, the percentic production, relative 

 to the growing stock, is fully 2 per cent larger in A, showing of how 

 little value the percentic statement is. 



The conclusion is that the inferiority in production of A is due 

 not to a lack of increment on the trees remaining, but to their deficient 

 number; the thinning was too severe. 



Another interesting showing results, namely, that while the total 

 average annual volume increment in A is smaller than in B by fully 

 10 per cent, the value increment in the two cases is nearly the same. 

 Percentically, however, both volume and value increment rjrc superior 

 in A, which might be considered an argument for the severer thinning. 



A similar comparison is made with the results in plot C, thinned 

 by 23 per cent. Here, as in ^. the average annual product in volume 



