WILLOWS AND POPLARS 225 



Sitka Spruce is another very fast-growing tree, and 

 though its height growth is somewhat similar to that of 

 Douglas Fir, it will not probably increase in girth measure- 

 ment at the same rate as Douglas Fir when growing under 

 similar conditions. However, the out-turn per acre should 

 be about half-way between that of Douglas Fir and of Silver 

 Fir. 



Cupressus macrocarpa is another tree which in suitable 

 localities should give a somewhat similar out-turn. 



Tree Willows and Poplars are very fast-growing trees, 

 especially the Black Poplars. These will produce a greater 

 quantity of timber in a short time than any other broad- 

 leaved trees. 



With reference to all the previous tables, it may be stated 

 that a greater final yield is in nearly all cases possible, by 

 restricting the thinnings in the latter half of any rotation. 

 But the adoption of such a course would result in committing 

 the common continental error of striving after maximum 

 final yields which, in most cases, results in a net monetary 

 loss, when compared with the results of crops which have 

 been somewhat heavily thinned, from the time that the 

 principal height growth was attained. 



The above data may all be represented graphically, both 

 as to volume or value, by dividing a circle into segments the 

 area of which is proportionate to the volume or value of the 

 thinnings removed at any time and of the final yield the 

 dates of the respective thinnings and their volume or value 

 are marked, as also are particulars of the final yield, in 

 their respective segments. 



[YIELD FROM STANDARDS OVER COPPICE. 



p 



