VOLUME AND YIELD, SECOND-GEOWTH 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 heav}' for its age. This is in part due to the 

 fertility of the soil and a very heavy annual rainfall, but probabl}^ 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 b}^ the mixture of species, knowledge of the rate of growth 



80,000 



70,000 



'50 60 70 60 30 lOO 110 120 /JO 140 150 

 AGL— YEARS 



Fig. 5.— Dingram showing yield per acre in board feet on a basis of age of pure even-aged Hemloelc, 

 with and without deduction for cull. 



will not suflice to foretell it unless the composition of the mixture is 

 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 umch 

 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, scrubliy, or otherwise unmerchantable trees has been 

 deducted. 



