REPRODUCTIOIT OF WESTERN YELLOW PINE. 19 



parts of the larger openings. Openings depend not only upon the 

 nearest seed trees along their borders, but upon all of the trees for 

 several hundred yards around. In high winds, yellow-pine seeds 

 may be carried as far as a quarter of a mile, but this is unusual. 

 Since the prevailing wind direction is from south to southwest, one 

 would naturally expect broader dispersal, but not necessarily denser 

 seeding, on the north side of a seed tree. This, however, is not a 

 matter of importance in a forest where seed trees occur on every 

 side. - What would be more valuable is a study of dissemination 

 throughout a stand. The nearest approach to such a study is a 

 seedling survey on sample plot 3a in September, 1919. Ordinarily 

 the results of such a survey would not be a good index to seed dis- 

 semination, but in this case it is thought to be fairly reliable, for 

 the reason that the rains during the summer of 1919 were so per- 

 sistent that seeds germinated everywhere, even on logs. The seedling 

 survey has an advantage over a seed survey in that it presents the 

 results in a more advanced stage. Table 8 shows that in a heavy 

 seed year the ground in Forest Service cuttings is abundantly seeded 

 at distances of 100 to 150 feet from the nearest seed trees. (See 

 also Fig. 1 for location of plots.) In other words, as far as seed 

 supply is concerned, it is permissible to make openings from 200 

 to 300 feet in diameter if they will be surrounded by a large number 

 of good seed trees. It should be borne in mind, however, that these 

 plots represent optimum conditions with respect to both the number 

 of seed trees and conditions for germination. 



From the standpoint of seed dissemination as well as seed pro- 

 duction, the ideal arrangement would be to space the seed trees 

 as evenly as possible over the entire area. Since the trees often 

 occur in groups to begin with, the ideal distribution can seldom be 

 attained. Nevertheless, the importance of location should not be 

 lost sight of. Other things being equal, a seed tree standing in the 

 middle of an opening is several times as effective as one standing 

 in a large group. 



FEEQTJENCY OF SEKD CROPS. 



Table 9 gives a record of seed crops and their results on sample 

 plots 3a and 3b, from 1909 to 1921. During this period three crops 

 were classed as " good " and one as " heavy, " and in six of the years 

 there was little or no seed. According to this record prolific seed- 

 ing occurs only once in three to five years. It is noteworthy that no 

 seed was borne in the years following the good crop of 1913 and 

 the heavy crop of 1918. No definite record is available for the year 

 1910, following the god crop in 1909, but it is known that a good 

 yield did not occur. 



