REPRODUCTION OF WESTERN YEM.OW PINE, 73 



cepting this conclusion, however, it must be considered that we are 

 dealing with a stand of seedlings which has originated under al- 

 most ideal conditions with respect to both seed supply and moisture, 

 and that therefore the figures on number of seedlings per acre must 

 be greatly discounted in order to be applicable to average condi- 

 tions. Moreover, 200 per acre at 10 years of age has been assumed 

 as a minimum standard ; 1,000 per acre would be very much better. 

 It is well before proceeding further to consider results on other 

 areas. 



Group II also lies in the region of the heavy 1918 seed crop and, 

 except for lighter grass cover, it is comparable to Group I. The 

 virgin forest in both groups contains very dense stands of 1919 

 seedlings. All the cut-over areas in Group II, however, were 

 logged under private management, which means that most of the 

 larger trees (yellow pine) have poor crowns. This condition is 

 strikingly prevalent on section 21. Another characteristic of these 

 cut-over areas is the uneven distribution of trees. It is common 

 to find openings 4 to 5 acres in extent bearing only two or three old 

 spike-topped trees. On plots 1a and 1b these conditions have been 

 avoided to a great extent. Results on these plots compare favor- 

 ably with those on the sample plots in Group I. The other two 

 cut-over areas, however, fall far below sample plot 1a and 1b, prob- 

 ably on account of a larger proportion of defective trees and poorer 

 distribution. The poor survival on plot 1 has remained unex- 

 plained until recently. Examinations in September, 1921, show that 

 the seedling plots are almost invariably situated in spots which are 

 unfavorable to survival. Considerable numbers of saplings occur 

 in irregular groups over most of the area. The seedling plots are 

 often near enough to these saplings to feel the influence of their 

 roots. Many of the seedling plots occur on clay flats, where repro- 

 duction is generally poor. The very fact that the plots selected for 

 seedling counts are in spots which have not restocked during the 

 past 20 years, although seedlings have come in all around them, 

 indicates that they are on unfavorable sites. Section 21 sustained 

 considerable damage from sheep grazing during tJie summer of 

 1920. 



Group III, in comparison with Groups I and II, shows clearly 

 the effect of seed supply. The areas in Group III occupy a better 

 site than the others, but the seed crop was much lighter. Here, 

 as in Groups I and II, the virgin stand shows a greater abundance 

 of seedlings than the cut-over areas. 



Group IV (sample plots 4a and 4b) furnishes a striking example 

 of the interdependence of rainfall and seed supply. Because of the 

 presence of a deep surface layer of cinders, pine seed germinates 

 poorly in seasons of average rainfall. Two fairly good seed crops 



