10 



sing as secondary species, according to the number of mature stems available 

 and the demand. Of the less valuable species in the second group it may not 

 be found possible to exploit them in the major fellings, though some may be 

 disposed of at a profit on permit in the improvement fellings. 



42. The period of felling is fixed at 40 years, during which time two 

 major felling series will be in progress, one on either side of the river, supple- 

 mented by four series of improvement fellings, two in each block, so that 

 during the felling period of 40 years each series of improvement fellings will go 

 over half the area of each block twice. 



43. To arrive at the age at which the four principal species attain their 



.,.,., respective exploitable girths, a large number of 



The yield or possibility. . , 8 m , ' , , f , 



sections was examined. The tabulated results are 



given in Appendix V. Great difficulty was experienced in counting the annual 

 rings of all these species, especially those in advanced age, so that it will be 

 necessary to leave throughout the calculations a margin of safety. 



44. One inch has been allowed on diameter for the bark of all species. 

 This is not actually correct for each individual species, as Matti would be more 

 than that. For Kindal and Nana it is about right, while the bark of Jamba, 

 especially of old trees, is less than an inch in diameter. However, if each 

 species were treated separately throughout, the calculations would be far too 

 complicated for practical application. A tree of 24 inches diameter with bark or 

 23 inches without bark will constitute a 6 feet girth tree with bark, and 27 inches 

 with bark or 26 inches without bark will constitute a 7 feet girth tree, the 

 measurements being taken 4| feet from the ground. 



45. From Appendix V it will be seen that the following are the rates of 

 growth of the four species : 



The time taken by the first three species to pass from 6 feet to 7 feet girth 

 varies somewhat. It takes Jamba, which is to be felled at 6 feet girth, 

 35 years to pass from 5 feet to 6 feet in girth. The average time it takes for 

 all four species to pass from their respective penultimate to their ultimate 

 classes is 38*2 years, and for safety's sake this figure is raised to 40 years. The 

 number of years it takes Matti, Nana and Kindal to reach 7 feet in girth is 

 respectively 195 years, 205 years, 175 years, and for Jamba to reach 6 feet in 

 girth 173 years. 



46. From the above figures it has been thought advisable to fix the 

 rotation, at 200 years, which is approximately that of Matti and Naua. If put 

 lower so as more nearly to sait Kindal and Jamba a certain number of the 

 other two more important species would not reach maturity within the rotation. 

 The effect on the possibility of Kindal and Jamba by raising the rotation will be 

 to slightly reduce the yield on paper of these two species. The effect in 

 practice will be very trifling and will constitute a margin of safety against over- 

 cutting. The 1st felling period has therefore been fixed at 40 years, and the 

 rotation at 200 years, which gives 5 cutting periods during the rotation. The 

 above calculations are based on rates of growth of trees in 1st quality areas ; for 

 the 2nd quality area, which covers only a small portion of the whole and where 



