VOLUME AND YIELD, SECOND-GROWTH HEMLOCK. 



43 



The character of three typical second-growth stands in Washington is 

 shown in Table 15, which is the result of surveys and measurements sim- 

 ilar to those made in mature timber and previously described. It will be 

 noted that in Willapa, where the mixture of Hemlock is most uniform, 

 the stand is unusually heavy for its age. This is in part due to the 

 fertility of the soil and a very heavy annual rainfall, but probably also 

 to the composition of the mixture, for a tract of given size can sup- 

 port a heavier forest of mixed Fir and Hemlock than of either species 

 alone. It is evident that, since the future yield of a second crop is 

 influenced by the mixture of species, knowledge of the rate of growth 



Ct 60,000 



O 

 CO 



^50,000 



30. 100 110 120 

 AGEL— YEARS 



130 140 150 



Fig. 5. — Diagram showing yield per acre in board feet mi a hasis of age of pure even-aged Hemlock. 



with and without deduction for cull. 



will not suffice to foretell it unless the composition of the mixture i^ 

 known. It is useless, therefore, to make hard and fast tables of future 

 yield for indiscriminate application to the varying growths which 

 may occur after logging. For a pure stand the problem is much 

 simpler. Fig. 5 represents graphically the stand which may be 

 expected from pure even-aged Hemlock near the coast of "Washing- 

 ton. It includes second growth only and not those trees which may 

 escape the first cutting. The upper curve shows the yield without 

 allowance for cull; the lower curve, the yield after 20 per cent for 

 dead, diseased, scrubby, or otherwise unmerchantable trees has been 



deducted. 



