SHORTLEAF PINE IN VIRGINIA 17 



WHAT TO REMOVE IN THINNING 



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Thinnings should remove such suppressed trees as are not 

 necessary to complete the crown cover, since they have made their 

 growth and exert little or no influence on the growth of the large 

 trees. Species of lower value, like gums, post oak, maple, sassa- 

 fras, and scrub pine, should also be cut, unless they are needed to 

 keep the crown cover complete. Punky or diseased trees should 

 be removed from stands of all ages. Short-bodied, crooked, 

 knotty, forked, or otherwise defective pine trees should be cut 

 from younger stands, but should be left in old stands when their 

 removal would make openings which would not be filled by the 

 spread of the surrounding crowns. P^nough of the intermediate 

 class should be removed to provide growing space for the trees 

 that are left. The trees which are removed should be selected 

 evenly through the stand. If several adjoining trees are removed, 

 an opening is left which will be too long in closing. If trees are 

 left in groups, excessive crowding in the interior of the groups 

 will follow, and this will result in the loss by shading of the in- 

 terior branches and unsymmetrical development of the trees. When 

 there is a choice the trees which are left for permanent growth 

 should have well- developed and symmetrical crowns. 



ACCELERATION IN GROWTH FROM THINNING 



Until they are thirty or even thirty-five years old, the inter- 

 mediate as well as the dominant trees of shortleaf pine stands re- 

 spond vigorously and rapidly to thinnings by accelerated growth. 

 In older stands, the recuperative power of the intermediate trees 

 declines and the recovery from the effects of overcrowding is slow. 

 The recuperative power of the dominant class, however, is main- 

 tained until the trees are sixty years old, when the period of rapid 

 height growth is well past and crown isolation has taken place. 

 The ability of the intermediate trees in young stands to recover 

 rapidly from the effects of close crowding, permits the cutting of 

 the largest trees in such stands and the leaving of the slender, 

 clear-stemmed intermediate trees to form the mature stand. 



In Plate VI, fig. 1, which shows the cross section of a stem 

 of shortleaf pine, is to be seen the results of accelerated and sus- 

 tained growth which are due to repeated light thinnings. The 

 crowded condition of the inner rings of growth show that the tree 

 was a slender, intermediate tree before its crown was freed by the 



