218 THE THEORY AND PRACTICE OF WORKING PLANS 



differences in the density of stocking: or (7) on need of artificial 

 reproduction. 



The minimum size of a subcompartment is i| acres. The 

 boundaries are marked with stenciled numbers painted in 

 oil color on the corner trees or else by means of symbols made 

 with a tree scribe; in young stands narrow alleys are cleared. 



Estimates and Forest Description. — As a general rule yield 

 tables are constructed for the various silvicultural methods of 

 management, species, and site classes, based on sample areas 

 measured during the progress of the field-work. The following 

 form is used: 



Column I. Age. 



2. Number of stems per hectare. 



3. Basal area at 1.3 M. above ground, in square 



metres. 



4. Average diameter at 1.3 M. above ground, in 



centimetres. 



5. Average height in metres. 



6. Average annual height increment in metres. 



7. Volume by timber classes, in cubic metres. 



8. Increment — current annual, in cubic metres. 



9. Increment — mean annual, in cubic metres. 

 10. Increment per cent — mean annual. 



These yield tables are compared with the published yield 

 tables of the International Association of Forest Experiment 

 Stations. 



The description of the individual stand covers the following 

 phases : 



(i) Soil and site. 



(2) Species, percentage of mixture and general form of the 

 stand. The percentage of mixture is expressed in tenths accord- 

 ing to the area occupied by each species. Shelterwood cuttings 

 are considered as preparatory if .8 of the original volume 

 remains; as seed cuttings if .5 to .8 remains; as removal cut- 

 tings if less than .5 remains. 



