6. There appeared to be more competition for the rootlets of the tree's main 

 laterals from roots of lesser vegetation than from the roots of other trees. Judicious 

 early thinning and application of selected herbicides might reduce this competition 

 from the undergrowth. 



7. The area contained within the perimeter of the primary lateral root ends is 

 not fully utilized by the tree. Because roots develop in soil where there are moisture 

 and nutrients (Kramer 1949), roots of neighboring trees can encroach into zones pres- 

 ently unoccupied. 



SUMMARY 



The root system of a 60-year-old, 67-foot-high ponderosa pine was excavated 

 for examination in central Idaho . Soil removal was achieved by washing and careful 

 picking. All main lateral roots were exposed, mapped, and measured. The taproot 

 and sinker roots were traced as far as hardness of the substratum permitted- -never 

 more than 50 inches. Secondary laterals were tallied by 5-foot lengths along the 

 main laterals. More than 3 percent of the primary and secondary laterals were 

 located between 6 and 24 inches beneath the ground surface. Ninety-eight percent of 

 secondary roots were 1 inch or smaller in diameter. Lengths of laterals varied from 

 45 to 797 inches. The root system extended over an area 5.4 times the size of the 

 projected tree crown. More of the root system grew on the downhill side than on 

 the uphill side. 



8 



