Part IV.] Caccia : Selection method of treatment in India. 381 
prescribing unequal sub-periodic returns (see Working Plan for the 
reserved forests in the Ihixa Division, Bengal, page 348 ante) ; or 
better still the reserve stock may gradually be built up in the manner 
explained below : — 
Nagkelu Kail working circle.* — The number of blue pine trees in this forest 
is as follows : — 
Class M — Over 2 feet diameter 908 
Class I — 14 to 2 feet diameter ..... 3,107 
Also a tree increases from I 4 feet to 2 feet diameter in 18 years. Supposing 
that only 90 per cent, of Class I reach exploitable dimensions, then every year 
on an average — ^-jg — - 155 trees become exploitable, and, with a felling 
rotation of 18 years, the normal exploitable stock on the ground is — 
X 18 X = 1,472. 
18 2 
There is thus a deficit of 1,472 — 908 = 564 trees. Hence for the present only 
- 564 
155 — — = 124trees can be felled. The crop in this forest is complete, as the 
lower classes are abundant, so that it is considered quite safe to fix the yield 
at 100 trees per annum. 
V . — The Crown Cover Method. 
The possibility under this method is taken to be equal to the 
growing stock whicli would be found standing on tlie oldest ago 
gradation if the selection forest in question were worked on the 
method of clearances and with the same rotation. In other words, 
the number of trees which become exploitable every year under the 
selection system should be ecjual to the number which would i;e 
obtained from the same forest worked on the method of clearances 
with the same rotation. 
The minimum girth or diameter of the exploitable tree being 
known, and the number of years {i.e., rotation) required to produce 
a tree of that size, the possibilit}' may be fixed as follows : — 
Let A = the wooded productive area of the selection forest. 
Let r = rotation or exploitable age. 
Let ff = the area covered by the crown of an average tree of the 
exploitable girth. 
* Revised Working Plan for the reserved forests of tlie Kotkhai and Kotguru 
fl-'iquas, Simla District, Punjab, by E. H. Coventry, I.F.S. , 1903. 
