30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



the data at Chacon are the closest legitimate record and must be 

 retained as they stand. 



The quality of the correlation between tree growth and March-July 

 rainfall at Chacon for the 33-year interval (table 15) is all that can 

 be ecologically expected considering the distance between Holman 

 Pass and Chacon, and considering the quality of the correlations be- 

 tween the rainfall of two stations approximately as far apart as 

 Holman Pass and Chacon. This suggests that the trees as a group 

 follow with a high degree of accuracy the fluctuations of rainfall at 

 the immediate site. 



In general, group 7 shows slightly higher correlations than the 

 others and group 5 slightly less ; otherwise there is little choice among 

 them. Group 4, the closest to Chacon, has a very slight advantage over 

 group 9, and both have higher correlations than group 5, which is 

 ecologically less similar to the other two than they are between them- 

 selves. In the case of groups 10 and 11, the former (from the drier 

 sites) has a slightly higher correlation than the latter although not 

 sufficiently so to justify any conclusions. Group 7, containing all 

 trees, possesses slightly better correlation than group 7 (restricted), 

 the values for March- July being 0.95 and (0.28) and for January- 

 August 0.94 and (0.19). 



Figure 4 shows Chacon rainfall for March- July compared with 

 tree grow^th of the several pertinent groups. 



The charted correlations of group 7 with Chacon rainfall in figure 6 

 indicate in general that the absence of summer rainfall and the pres- 

 ence of winter rainfall militate against high agreement. It is neither 

 spring rainfall alone nor spring combined with winter rainfall which 

 gives highest correlations but spring added to early and midsummer 

 rainfall. 



Tree growth (individual trees) and Chacon rainfall. — Individual 

 trees were correlated with the two rainfall intervals of March- July 

 and January- August (table 16). The results are to be expected, no 

 doubt, in view of the former group correlations. In general, the trees 

 agree a little better with March- July than with January- August rain- 

 fall. Tree HPC 3, a foxtail pine, has the highest correlation and 

 HPC 9, a ponderosa pine, has the lowest. However, HPC 5, a 

 Douglas fir, runs a close second to HPC 9. As a matter of fact, tree 

 HPC 3, which stands between HPC i and 2, could be used as a fair 

 substitute for group 7. Ponderosa pines have no advantage over the 

 other species. On the whole, the trees east of the Pass correlate better 

 than those on the Pass and these latter slightly better than those 



