dard tables.* The degree to which these sites are understocked varies ac- 

 cording to the management regime which is chosen based on the objectives of 

 the land owner or manager. 



If the average forest acre is understocked, the average amount of basal 

 area per acre may actually be low for all owners on all site classes. Thinning 

 opportunities would still be available, but at a level below the initial estimate. 

 Evidence of understocking would indicate that there are areas where stocking 

 needs to be increased by natural or artificial regeneration if higher yields are 

 desired. 



The graphs in Figures 10 and 11 represent a one-point-in-time picture of 

 the average basal area per acre by diameter class. The key to developing 

 timber management strategies based on these graphs is to know the direction 

 and rate of change occurring within each diameter class. Estimates concern- 

 ing the changes or dynamics of the forest can best be made by analyzing 

 remeasurement data. Unfortunately, such data is not available at this time. 



*For example, according to basal area standard tables for ponderosa pine 

 (derived from USDA Technical Bulletin No. 630, 1934), 80-year-old stands on 

 MAI sites of 30 cubic feet per acre per year should have a basal area stock- 

 ing of 93 square feet per acre. Ninety-year-old stands on MAI sites of 60 

 cubic feet per acre per year should have a basal area stocking of 135 square 

 feet per acre. 



-53- 



