KEPRODUCTION OF WESTERN YELLOW PINE. 



83 



where by thinnings increased growth 

 from trees left can be obtained, or 

 where because of defect, disease or 

 insect infestation, forest conditions 

 can be improved by their removal. 

 By intermediate trees is meant fast 

 growing trees in the transition stage 

 from blackjack to yellow pines. 



Seed trees, whether left singly or in 

 groups, should be as well distributed 

 as possible, so as to seed the maximum 

 area. The best seed tree is a blackjack 

 or intermediate tree over 22 inches d. o. 

 b., wind firm, sound and free from me- 

 chanical or fungi defects, with full 

 healthy crown and showing evidence of 

 bearing cones. Its physical location 

 from the standpoint of the area it will 

 possibly seed should also be considered. 



Note. — These instructions in so far 

 as they are in conflict with those given 

 on pages 36 to 44 of the Silvicultural 

 Handbook, supersede the latter. 



It is usually unnecessary to consider 

 the factor of protection on north 

 slopes, moist locations, or areas where 

 the soil is protected by oak brush or 

 other living brush or reproduction. It 

 should uniformly be considered on 

 wind-swept areas, slopes exposed to 

 drying-out influences of sun and wind, 

 cinder soils, and dry locations where 

 any form of protective cover is absent. 



Wind-swept areas. 



the future growing stock rather than 

 to seed production. 



Yellow pine, because of larger size, 

 produces more seed per tree than black- 

 jack, but involves more risk from wind- 

 fall, lightning, and the general deteri- 

 oration associated with old age. 



In view of recent findings in regard 

 to seed production, exception might be 

 taken to the statement that blackjacks 

 or intermediate trees make the best 

 seed trees. Yellow pines produce more 

 ' seed than blackjacks, but because of 

 the greater desirability of the latter 

 as growing stock, they should be given 

 the preference, with the understand- 

 ing that a greater number will be re- 

 quired. In practice, however, the ideal 

 seed tree is difficult to find, and often 

 it is necessary to leave some trees 

 which fall below the highest standard. 

 The usual grouped arrangement is not 

 conducive to efficient seed production 

 or dissemination. For this reason, 

 increased use of thinnings in dense 

 groups of blackjack is recommended. 

 Thinnings within groups must, how- 

 ever, be made with due regard for 

 windfall and damage to remaining 

 trees in felling. 



In accordance with the old concep- 

 tion of the role of protection, we find 

 this idea emphasized throughout the 

 instructions. The second footnote 

 specifies the conditions under which 

 shelter of standing trees should be 

 made a primary consideration in cut- 

 ting. Analysis of these conditions in 

 the light of recent investigations is 

 profitable. Specific reference is made 

 to " wind-swept areas," " slopes ex- 

 posed to drying-out influences of sun 

 and wind," " cinder soils," and " dry 

 locations where any form of protec- 

 tive cover is absent." 



Areas exposed to unusually high 

 wind movement undoubtedly warrant 

 leaving a sufficient number of trees 

 to break the force of the wind. In 

 all excepting the most extreme cases, 

 this will be accomplished by the num- 

 ber of trees usually left, that is 10 to 

 12 trees per acre above 11 inches di- 



