148 COLONIAL REPORTS MISCELLANEOUS. 



C. The Collection of Data for the Preparation of Working 



Plans. 



This very important work should be undertaken concurrently 

 with the exploration and selection of areas for reservation. In 

 the early stages of forest conservancy in tropical West Africa, 

 it will not be possible to undertake any refined and costly 

 measures of this sort, but simple and approximate methods of the 

 nature indicated below should invariably be adopted with a view 

 to supplying some information regarding the actual condition 

 of the growing stock in the forests, and for the purpose of framing 

 simple and safe prescriptions for their exploitation till such a 

 time as more detailed and accurate systems become possible. 

 Reserves should invariably be exploited under some such simple 

 prescription, that limits the fellings to a definite proportion of 

 the mature timber they contain. For example, a prescription 

 that limits the fellings during a specified period to one-third, 

 say, of the number of mature trees standing in the reserve is 

 both simple to understand and to apply. It merely means that 

 o\it of every three mature trees found in the forest, one is to be 

 marked for felling. The person selecting the trees to be cut 

 searches about in the forest and marks every third tree of the 

 requisite girth that he comes across, and has them felled. If 

 with such a prescription is combined the 'observance of simple 

 rules that prohibit the felling of isolated trees of a particular 

 species, and further limit the first choice to trees that are past 

 their prime as seed-bearers, little or no harm will be done to the 

 forests by the time that they can be placed under a more rigorous 

 and accurate treatment. In any case it is much to be preferred 

 to the ordinary haphazard methods that do not take into con- 

 sideration the actual condition of the growing stock. 



Before a simple plan of the nature indicated above, however, 

 can be framed, it is necessary to ascertain :- 



'() the rate of growth, of the particular species exploited, 



at definite periods of their age ; and 

 (1>) the proportion (in number of trees) existing between the 



various age or girth classes. 



As regards (a) the rate of growth : The Vjest and safest method 

 of ascertaining this, with respect to any particular species, is to 

 actually measure at regular intervals, say, of three, four, or 

 five years, the girths or diameters of a good representative series 

 of individuals of all sizes from that of the sapling to the mature 

 tree. The same trees should be re-measured at the end of every 

 third, fourth, or fifth year, as the case may be, and the process 

 continued till 15 or 20 years have elapsed, by the end of which 

 time it will be possible to obtain reliable data as to the rate 

 of diameter urowth of the species during the different stages of 

 its growth. The latter is not uniform in rate throughout the 

 lifetime of any particular species, hence the necessity for includ- 

 ing individuals of all sizes (the girths are proportional to the 

 ages) amongst those measured. 



If the measurements are made on series of trees growing on 

 poor, middling, and good soil, more accurate data still will be 



