REPRODUCTION OF WESTERN YELLOW PINE. 81 



might be classed as an average "good" crop, however, renders the 

 results reasonably conservative. This area has 3.8 seed trees over 

 20 inches in diameter per acre. Fewer seed trees would mean fewer 

 seedlings at the present stage, which would clearly not be desirable. 

 We may say then, in answer to the question. ;; How many seed trees 

 per acre are required?" that for average stands we should count on 

 leaving at least four trees over 20 inches diameter breast high. This 

 is an average figure which calls for variation with the character of 

 the site and stand. As will be explained in the discussion of mark- 

 ing practice, more trees will be needed on adverse sites. If the trees 

 are large, running well above 25 inches in diameter, and of good 

 crown development, the number may be reduced to 3 per acre. On 

 the other hand, if the trees are mostly small (below 25 inches) and 

 of mediocre crown development, as is likely to be the case if they 

 occur in large groups, more than 4 may be needed. 



Having established as a minimum the requirement of four seed 

 trees per acre for average sites under the group selection method, 

 we may again refer to the question raised in the discussion of 

 Group I. as to whether areas such as sample plots 3a and 3b are 

 not provided with more seed trees than are really necessary. Plot 

 3a has 5.2 and plot 3b 7. c trees over 20 inches in diameter per acre. 

 Results during the 10 years prior to 1919 do not suggest a surplus 

 of seed. Inspection of these two plots shows that many of the 

 seed trees are relatively ineffective. In plot 3b they consist en- 

 tirely of blackjack, which are mostly in groups, and a large propor- 

 tion are diseased, due to mistletoe infection. Plot 3a has a good 

 representation of free-standing yellow pine, but many of these 

 are decadent and are not producing normal quantities of seed. 

 Eliminating the unproductive and poorly situated trees, the margin 

 above the specified minimum of four good seed trees per acre will 

 shrink to a negligible quantity. 



Great emphasis must be placed on quality and location as well 

 as upon the number of seed trees. In many virgin stands there 

 is a dearth of good trees so located as to give proper distribution of 

 seed. In such cases it is better to fall below the standard require- 

 ment than to leave poor trees which sap moisture from the soil but 

 yield negligible quantities of seed. A fact which heretofore has 

 remained unnoticed, but which has been clearly demonstrated by 

 the scattered seed-tree cutting, is that stump patches created by 

 clear cutting in groups afford the best pos-ible opportunity for 

 immediate replacement of the trees which are removed. To secure 

 the best results the groups should be cut clean, and seed trees should 

 be left where they will seed these spots without invading them with 

 their roots. 



904°— 23 6 



