Table 7 . --Comparison of the mean 10-year oumutat-Lve radial increment between mature 

 ponderosa pine trees of different risk ratings in western Montana 





Number 



• Mean increment 





Plot : 



of trees 



: Risk 1 : 



Risk 2 • Risks 3 and 4 





sampled 



• trees 



trees • 



trees ^ 









- - -Inch - - - - - 





A 



212 



0. 37 



0.23 



0.15 



B 



90 



.43 



.36 



.19 



C 



38 



.49 



.35 



.19 



D 



43 



.43 



.30 



. 20 



Average 





.43 



.31 



. 18 



Number of trees 











in Risk group (s) 





143 



168 



72 



■^These two ratings 



were pooled 



for statistical analyses. 





When compared with 



data reported by Spencer (1953) 



, these means exhibited a progre 



sive decline in value from trees rated Risk 1 to those 



of the pooled Risk 



3 and Risk 4 



trees (table 7) . This 



statistically 



significant reduction in growth rates 



confirmed th 



poor vigor of trees rated Risk 3 and 



Risk 4. This reduction had been susp 



ected because 



the risk rating system 



identifies trees having weakened 



or decadent crowns 







Mean Volumes of Risk Rated Trees 





The mean gross volume of the 11,946 sawlog-size risk-rated trees was 



776 board 



feet. The mean volume 



of Risk 1 and 



Risk 2 trees was less than this value 



; that of 



Risk 3 and Risk 4 trees 



exceeded it , 



as shown in tlie following tabulation: 







Number of 



Volume of risk 



Mean volume 





Risk 



risk rated 



rated trees 



per tree 





ratings 



trees 



(Board feet) 



(Board feet) 





1 (Low) 



1,536 



787,260 



512 





2 (Moderate) 



8,628 



6,640,970 



770 





3 (High) 



1,533 



1,583,390 



1,033 





4 (Very high) 



249 



264,740 



1,063 





Total 



11 ,946 



9,276,360 



776 





20 



