16 



understood, it is necessary that these facts should be stated 

 and the manner in wliich the prescriptions have been 

 deduced from tliem explained. These facts, deductions, and 

 prescriptions are recorded in a single report which, although 

 usually embodying several separate plans, is generally, for 

 conciseness, called the working- plan of the whole area dealt 

 with. 



3. Meaning of the term "sustaiued yield/' — A sustained yield 

 is a perpetual {"sustained") periodic outturn of timber, fuel, 

 bamboos, etc, resulting from a systematic treatment of the- 

 forest crop. When, in addition, the crops ar« so arranged 

 that regular supplies of produce approximately equal in 

 quantity are obiained year by year (or periodically) the- 

 forest is snid to produce an equal annual (or periodical) 

 sustained yield. 



A sustained yield will be obtained fi'nm a forest which is so worked that it wilh 

 continuously produce crops of wood : each portion as it is cleaveJ being restocked^ 

 within a reasonable time and the young woods which spring up being properly tendei- 



Section II. — Ihb normal forest. 



1. JJfaning'of the terra.— It has been stated that the chief 

 purpose of a working-plan is, generally, to secure the condi- 

 tion of crop that is necessary in order that the forest may 

 yield perpetually a regular supply of produ«e in greatest 

 qufiiitity, or, as it is called an equal annuil or periodic 

 sustained yield. In order that an an'^ual sustained yield 

 may be obtained it is necessary that the forest should be 

 constituted of a series of growths of all ages from the seed- 

 ling to the exploitable tree, that is, of a series of age-srada- 

 tions corres ponding to the number of years in the exploitable 

 age. li", in addition, an equal annual sustained pield is 

 required, the age-gradations should occupy equnl or equi- 

 productive areas, each one beins cooipleteiy sti eked with 

 sound, vigorously-growing trees, yielding a full annual incre- 

 ment coi responding to the age of the crop. A foiestin 

 which these conditions exist, tlat; is, a forest which has (a) a 

 normal series of age-grad.itions or age-classes, (6) a normal 

 increment, and consequently («) a normal grnwins st «k or 

 forest crop is termed a normal forest. It follows tliat there 

 is nothing' absolute in the term. A forest normal under one- 

 nietliod of treat uent or ;ige of exploitation would be abnormal 

 under any otder treatment or age. 



In a normal forest the quantity and quality of th& 



