210 
Indian ForeBt Recordt. 
[VoL. L 
The age at which the mean annual volume increment of a whole wood 
culminates is of great importance as indicating the rotation of greatest 
production of volume : but data are not available for the Sal, and owing 
to the absence of even-aged woods, the problem as far as it relates to 
seedling forests must for the present await solution. 
For woods under regular coppice treatment figures might no doubt 
be collected within a short period of time : a question which is now 
receiving attention. 
In the Nawabganj forest of the Gonda Division, coppice woods 19 
years of age were found to yield an average of 550 cubic feet per acre after 
retaining 60 shoots to the acre : average size of shoots being 6 inches 
in diameter. 
Section 7. — Thinnings, 
Thinnings, according to their intensity, have a very great influence 
on the development of the volume of whole woods.* The question is 
stdl under investigation in Europe, and onlj^ a limited number of data 
are available. It has been shown that in open woods, height increment 
is greater than in crowded woods ; but it decreases at an earlier age and 
the trees are more apt to develop low side branches. Heavy thinnings 
are not theiefoie advisable before the time when a suitable length of 
bole has been formed. Thinnings again (see table below), have a very 
decided influence on the development of the diameter, which so largely 
affects the value of a tree, whilst their effect on the volume of a crop 
appears to depend chiefly on species and age. It has been proved in 
Europe that judicious thinnings may cause the volume increment per 
cent, to increase by as much as 25 per cent, to 100 per cent. As a 
result the age at which the volume increment culminates may be 
raised, permitting of the adoption of a higher rotation without any loss 
in the final major yield : but data showing the effect of thinnings on the 
volume increment per cent, of Sal are not available in India. 
The total yield of a crop at any age consists of the final yield occur- 
ring in that year plus the volume of the intermediate cuttings or thin- 
nings. The proportion between final and intermediate yields has not so 
far been ascertained for the Sal. Neither have data been collected to 
show the volume of the intermediate cuttings that may be expected 
from Sal woods at different ages, or the percentage of final and interme- 
diate yields for different rotations. The volume yield of the interme- 
*Jacquot’.^ '‘Jncendies en Foret, ” page? 248 to 263, should be consulted. Also 
aseries of articles by Emile Mer on '’'L' influence de I'iclaircie descipiea sur ia croissancedts 
Tejets, ” Eaux et Forfits, 1907, Nos. 11, 12, 13, 14. 
