512 



NATURE 



[April 2, 1896 



Voltiinc and Vobnne-increment of Timber down to 3 inches 

 diam. Net value and Vahte-increiiient. All on one Acre, 

 stocked with Scotch Pine of middling quality. 



Age, years 60 70 80 90 100 



Number of trees per acre ... 516 393 316 266 230 



Mean height, feet 51 57 63 67 71 



Volume, cubic feet, solid ... 3713 4183 4587 4902 5158 

 Current annual increment, 



cubic feet, solid 47"o 40"4 3i"5 25-6 



Volume increment, per cent. i"2 0*93 o*6o 0*51 

 Net value pf stock (shillings) 1 186 1683 2225 2789 3376 

 Volume- and value-incre- 

 ment, per cent 376 283 2-29 1-93 



If two woods, known to be 60 and 100 years old, have 

 a mean height of 5 1 and 7 1 feet respectively, it follows 

 that they belong to the class, of which an extract is here 

 given, which is known as the third or middhng class, 

 and, if completely stocked, the volume standing on one 

 acre would be 3713 cubic feet in the one, and 5158 cubic 

 feet in the other case. Other Scotch pine woods of the 

 same age, if their mean height were greater, would belong 

 to a higher quality class, and if fully stocked, their volume 

 would be that recorded in the yield tables under their 

 class. It stands to reason that in woods not fully stocked 

 the timber per acre is less in inverse proportion to the 

 degree of completeness. 



The great practical importance of height-growth will 

 perhaps be better understood by reference to matters 

 which, many years ago, have exercised considerable 

 influence upon the development of regular forest manage- 

 ment in India. The writer of these lines, on taking 

 charge, in January 1856, of the Pegu teak forests, made 

 it his first duty to ascertain which were the most valuable 

 forest tracts in that country. The number of teak trees 

 of the dififerent age classes on the square mile, he ascer- 

 tained by a system of linear valuation surveys, laid 

 through the forests in all directions. At the same time 

 he measured the height of trees in all districts. The 

 data thus obtained, the timber standing on the ground, 

 and the height of the trees, particularly of the younger 

 classes, enabled him to classify the forests, and to pick 

 out those which were the most valuable. The measures 

 which he had introduced, had gained him the confidence 

 and goodwill of the Karen and other inhabitants of the 

 forests, for those measures gave to the people profitable 

 employment in timber operations, and this made them 

 allies, instead of enemies, in regard to forest protection. 

 The merchants of Rangoon, on the other hand, naturally 

 desired to get the forests into their own hands, and, backed 

 by the influence of the powerful mercantile firms of 

 Calcutta, they induced the Government of India to order 

 the Pegu forests to be thrown open to private enterprise. 

 These orders had to be carried out ; but, fortunately, 

 they did not require that the whole of the forests should 

 be thrown open at once. Those districts, therefore, in 

 which the growing stock of teak timber, in regard to 

 height and otherwise, was most promising, were for a time 

 retained under control of the Poorest Department, while 

 the rest were thrown open to private enterprise, in 

 accordance with the orders received. This was in 1861. 

 Subsequently a different view of the question was taken 

 by Government ; the arrangements which had been made 

 could not, however, be cancelled. The mischief had 

 been done ; but, fortunately, it had been limited to the 

 less valuable districts. The really valuable forests, which 

 had been reserved in 1861, had been saved, and this 

 made it possible to maintain a profitable system of 

 regular management. 



The little table, entered on page 511, illustrates the 

 growth of a Scotch pine wood of middling quality 

 between the ages of sixty and a hundred years. As the 

 wood advances in age, the number of trees diminishes, 

 but the remaining trees are taller and heavier, and hence 

 the total volume mcreases. During these 40 years no 



NO. 1379, VOL. 53] 



less than 286 trees have died or been thinned out, and 

 the skill of the forester consists in this, that the final crop 

 is composed of sound and well-shaped trees, so that their 

 timber may fetch the highest price obtainable. These 

 figures show further, that, while in the first period of 10 

 years, between 60 and 70, the timber produced per acre 

 amounted to 470 cubic feet, or 47 cubic feet a year, only 

 256 cubic feet, or 25"6 cubic feet annually, were produced 

 from the 90th to the looth year. 



The current annual increment is greatest while the 

 forest is young, in the case of Scotch pine between the 

 ages of 30 and 40, after which it diminishes steadily. 

 The annual increment may be regarded as a percentage 

 of the growing forest capital. Between the years 60 and 

 70 the increment per cent, {p) would be determined by 

 the formula : 4183 = 3713 x vop^''\ which makes/ = V2. 

 Between the years 90 and 100 the increment per cent, is 

 only o'5i. The maintenance of a forest, which increases 

 at a rate so slow and so steadily diminishing, at first sight 

 appears to be a most unprofitable undertaking. Fortu- 

 nately the market value of the timber up to a certain point 

 increases with the age of the wood. The net value of 

 the growing stock (less the cost of cutting, carriage, and 

 other expenses) of the wood exhibited in the table at the 

 age of 60 years is 1186 shillings, rising to 1683 shillings 

 at the age of 70. During this period the value- and 

 volume-increment per cent, is 376, but it falls steadily to 

 1-93 per cent, between the years 90 and 100. Obviously, 

 from a purely financial point of view, it is best to cut the 

 wood when it is between 80 and 90 years old, and to in- 

 vest the proceeds in Consols at ih per cent., for its main- 

 tenance beyond that age entails a loss of interest. The 

 increment, that is the interest on the growing capital of 

 the forest, is less than can otherwise be obtained on 

 perfect security. 



It is also evident that the value- and volume-increment 

 per cent, may be used to aid in determining the most 

 profitable rotation to adopt in the management of a 

 forest. In the vicinity of coal- or other large mines, where 

 pit-props find a ready sale, a rotation between 60 and 70 

 years, and even lower, would be most profitable. Where, 

 however, the chief demand is for building timber, or 

 there is a risk lest an over-production of smaller wood 

 might lower prices, the rotation should be higher, 70 to- 

 80 or 80 to 100 years. The value- and volume-increment 

 per cent, does not, however, correctly express the rate at 

 which the forest capital works. For this purpose the 

 formula must be completed by inserting the annual ex- 

 penses for taxes, administration, &c., as well as the rent 

 of the soil. The result is called the forest per cent. To 

 discuss this part of the subject would, however, lead too 

 far on the present occasion. 



Part ii. deals ^'x'Ca. forest valuation. Obviously it 

 is often necessary, when a forest is to be divided, or 

 assessed or sold, to determine its capital value. The 

 English reader may be disposed to think this an ex- 

 tremely simple matter. The value of a piece of property 

 is either its selling value or its productive value, and 

 these can readily be ascertained by the prices paid for 

 forest land in the open market, or by the rent derived 

 from forest land. Sales of forest land, however, do not 

 often occur, and when a sale takes place, the price 

 realised for one piece of forest does not give the value 

 of another piece. Soil, aspect, elevation, and the other 

 factors which influence the annual timber production 

 and the rate at which the timber can be sold, must be 

 considered, and more than these, the actual condition 

 of the growing stock depending upon species, age, and' 

 previous treatment. 



Nor does the rental of forests come to our aid ; forest 

 lands, as a matter of fact, are not often leased out, the 

 difficulty being to make sure that the capital value of a 

 forest has been maintained unimpaired during the lease. 

 The rent obtainable from a field, or from a piece of grass- 



