Figure 6. — Heavy shadzng 

 by the Tamarack Hill 

 shelterwood stand 

 favored growth of 

 western hemlock 

 and suppression of 

 less tolerant species. 



ml 



Tamarack Hill: Shelterwood Block 



Description 



This 27-acre tract is located on a steep north slope. The entire area is Thuj a - 

 Tsuga/Pachistima habitat type. In 1935 and 1936, two overstory treatments were applied, 

 both of which resulted in nearly pure western white pine shelterwood stands. One half 

 of the tract (area 3a in fig. 1) contains hemlock and grand fir trees that were all 

 highly defective or otherwise unmerchantable; these were felled and the slash was piled 

 and burned. On the other half (area 3B) , fir and hemlock larger than 8 inches d.b.h. 

 were girdled, smaller stems were felled, and the slash was piled and burned. The 

 reserve stand permitted only an estimated 50 percent of full sunlight (fig. 6), beneath 

 the canopy on the area where all of the low-value stems were felled. Under the canopy 

 where girdling had been done, the light probably was even less for several years, but 

 it approached the same intensity after the girdled trees died and began to deteriorate. 



Results 



Four years after logging, stocking of the combined species on this area was above 

 80 percent, and by the eighth year stocking exceeded 90 percent (figs. 7, 8) with 

 13,000 seedlings per acre. Regeneration was most rapid on the portion of the area 

 where all of the low-value trees were felled, but it seems likely that this was due 

 more to a favorable location with respect to adjoining seed sources and the prevailing 

 wind than to the nature of the treatment of unmerchantable overstory. 



At the end of the period of record, hemlock and grand fir, though virtually elim- 

 inated from the shelterwood stand, far outnumbered western white pine in the 

 regeneration . 



The disturbance caused by logging the residual overstory on half of the area in 

 1952 reduced stocking of all-species from 100 percent to 86 percent. Losses were great- 

 est among the western white pine, grand fir, and larch reproduction. 



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