

54 PRACTICAL FOREST MANAGEMENT. 



statistical research has first and foremost to supply a 

 clear definition of quality. 



(d) The quality classes. For' species of trees with annual 



rings, the quality classes are usually defined by the 

 varying heights for definite ages, while for other species, 

 whose ages cannot be readily determined, no really 

 satisfactory basis of definition of quality classes has yet 

 been found, except the maximum height of trees or 

 crops at maturity. 24 



(e) Determination of " reduced equal areas. " -The potential 



volume production between different qualities of locality 

 vary greatly, and when a sustained equal annual yield is 

 aimed at, it becomes an important matter of practical 

 forest management in a forest of varying qualities 

 to reduce the areas to a common basis of potential 

 production. 



Statistical research alone provides the data for this. 

 (/) Volume figures for single trees. In addition to the above 

 data, statistical research also supplies complete infor- 

 mation regarding the volume and outturn of timber, 

 firewood, branchwood, bark, bole, etc., etc., as well as for 

 determining annual volume yields. 



When sufficient statistical data have been collected, the 

 results are summed up in the production of Yield Tables and 

 Volume Tables, which are described below and the methods 

 employed in collecting the necessary data are given in the next 

 section. 



Collection ^ n ^ s mav De divided into two heads 



calcula- ( a ) -^ or evenaged fully stocked crops, or yield tables. 



Statistical ( & ) For sin g le trees > or volume tables. 



data,. 



" For method of defining quality classes in tal, see Smythies' and Howard's Types and Distribu- 

 tion of Sal Forests in the United "Provinces. 



