Part II.] 
Caccia ; Development of Sal. 
Section 5. — Basal Area Increment. 
209 
Laws which govern the basal area development of whole woods in general : — ■ 
I. The total basal area of a whole wood is very small at the commence- 
ment : but it increases continuously during the whole period of the 
crop’s existence. 
II. The basal area increment depends largely on the growing space neces- 
sary for the proper development of the species, and on the quality 
of the locahty. 
III. The greater the growing space required, and the poorer the locahty (not- 
withstanding the larger number of stems) the sooner will the basal 
area increment begin to decrease. 
The basal area of a whole wood is equal to the sum of the basal areas 
at breast-height of the several individuals constituting the crop. But, 
since the number of stems per acre may vary without appreciably affect- 
ing the basal area of the whole wood, it follows that the latter is not pro- 
portionate to the number of stems per acre. Nevertheless, other factors 
being equal, the greater the number of stems, the greater the basal area 
of the whole wood. Data specially relating to the Sal are not, however, 
available. 
> 
Section 6, — Volume Increment. 
Laws ivhich govern the development of volume increment oi whole woods in 
general : — 
I. The total volume of a whole wood is very small during early youth, and 
it increases slowly. Towards middle age it begins to rise very 
rapidly ; but later on the annual increment steadily continues to fall 
until the death of the wood, without however ceasing altogether, 
except through disturbing factors. 
II. The current annual increment of a whole wood rises rapidly after the first 
youth is passed, and as a rule eulminates towards middle-age (50 to 
100 years), or even later, exeept in very favourable localities and in 
r : fast growing species when it may culminate at a very early age (be- 
tween 30 and 40). After reaching its maximum the cixrrent annual 
increment falls, rapidly under favourable conditions, slowly in poor 
localities. 
III. The mean annual increment of a whole wood keeps below the current annual 
increment until the two become equal : it then culminates, and 
thereafter slowly falls, though remaining greater than the current 
annual increment. 
IV. — The progress of the volume increment 'per cent, for a whole wood is 
analogous to that of a single tree. It is very high during the early 
youth of the wood ; it then diminishes very rapidy ; and subse- 
quently more slowly until absolute maturity is reached. The volume 
increment per cent, appears to vary only slightly between species. 
