Table 6. --Relationship between the abundanoe of high risk ponderosa pine 

 trees and some soil characteristics in western Montana 



Number ; 



of : 

 plots : 



Percentage of • 



Risk 3 and 



Risk 4 trees '. 



in the stand 

 1 — 



Soil '. 

 fertility '. 

 rating class ^ ; 



Soil 

 productivity 

 site index^ 



Water-holding 

 '. capacity^ 











Inches 



5 



7-12 



1 



66-71 



12-16 



4 



13-18 



2 



54-71 



6-12 



2 



19-21 



3 



54-60 



5-6 



4 



22-25 



3-4 



54 



5-6 



^Relative rating of soils between plots; based on chemical and physical 

 properties of the soils and their ability to supply plant nutrients. Class 

 1, high; classes 2 and 3, moderate; class 4, low. 



measure of productivity under specified management practices. Tree 

 height at 100 years CMeyer 1938) . Correlated with information from Cox and 

 others (1960) . 



^As measured in top 5 feet of soil. 



Risk Ratings and Soil Ctiaracteristics 



The preliminary method of soil examination used by McConnell^ on 15 of the plots 

 in 1966 disclosed that the incidence of high risk pine trees in the sampled plot stands 

 was associated with several soil characteristics. Increasing percentages of pooled 

 Risk 3 and Risk 4 trees were closely related to (1) decreasing soil fertility rating 

 classes, (2) soil productivity site classes, and (3) inches of water-holding capacity in 

 the top 5 feet of soil (table 6). 



A general relationship was indicated between the abundance of high risk trees and 

 the following factors observed or measured in the preliminary soil examinations: 

 (1) Soil depth to gravel-sand or bedrock; (2) texture of profile; (3) underlying soil 

 material; and (4) related soil series. 



No apparent relationship was indicated between the abundance of high risk trees and 

 the following factors: (1) Depth to water table; (2) elevation, slope, or exposure; 

 (3) landform; (4) mean annual precipitation or F-degree temperatures of the nearest 

 meteorological station; (5) precipitation-evaporation transpiration index; or (6) wind- 

 throw and windthrow physiography. 



Risli Ratings and Tree Growtli Rates 



The increment cores taken from basal bole sections of the 383 trees were measured 

 for the years 1944 to 1953, the most recent 10-year growth period. The mean cumulative 

 width of the annual rings for the period, 1944 to 1953, was calculated in inches for 

 each core group on each plot. The value derived is expressed as the mean 10-year 

 cumulative radial increment. 



Op. cit. 



19 



