NOTES AND COMMENTS 357 



evenly distributed ; where they are arranged in big groups the increased 

 growth is very sHght. 



4. Healthy crowns produce accelerated growth abundantly, whether 

 the trees have been dominant or suppressed, but all trees with imper- 

 fect and unhealthly crowns produce practically no increased growth. 



5. Accelerated growth normally begins two years after cutting, 

 lasts 30 to 40 years, and has a regular life habit. 



With regard to windfall 



1. Wind storms severe enough to throw trees in cut-over stands 

 occur periodically, perhaps as frequently as once every four or live 

 years, and these storms occur universally in the eastern portion of the 

 Blue Mountains. 



2. Heavy selection cuttings in which only about 8 per cent by 

 volume of the trees are left standing suffer as greatly from windthrow 

 as lighter selection stands in which 25 or 30 per cent are left standing. 



3. A heavy windthrow probably takes place in most selection cut- 

 tings in the Blue Mountains, which in 20 years may amount to as 

 much as 25 per cent by volume of the entire reserved stand. Of this 

 windthrow the greatest per cent by volume of the trees are blown down 

 by the first severe wind storms which strike the stand immediately 

 after cutting. In this way 60 per cent of all the trees which are blown 

 down in 20 years may be thrown in the first five years following cut- 

 ting, and the remainder thrown in rapidly decreasing percentages year 

 by year until 15 or 20 years after cutting, when the windthrow becomes 

 normal, or about what it is in the virgin forest. 



With regard to reproduction 



1. Yellow pine reproduction on cut-over areas in the Blue Moun- 

 tains is remarkably abundant and well distributed, and is amply suffi- 

 cient for adequate reforestation. 



2. On cut-over areas, as a whole, advance reproduction is more 

 plentiful than subsequent, both in total number and number of 

 dominants. 



3. Subsequent reproduction grows two or three times as fast as 

 advance reproduction in the virgin forest, but advance after cutting 

 increases its height growth, and in most cases maintains its lead over 

 the rapidly growing subsequent. 



4. Malnourished or suppressed advance reproduction recovers after 

 cutting, and where the cutting is heavy enough a high percentage of it 

 makes thrifty reproduction. 



5. The reserved stand seems to have very little effect on the abun- 

 dance of reproduction, and its effect on the growth and vigor of repro- 

 duction does not appear to be serious when the stand is below 30 per 

 cent, but under a heavier reserved stand the reproduction grows much 

 less rapidly. 



