H.—3

4

of practical forestry ;* but, besides the conservation of a forest as a whole, it is also necessaiy to determine the annual quantity of product which this forest is capable of supplying in perpetuity. This is scientific forestry. The method of disposing of the produce of high timber forests by superficial measure of the land has, long ago, been replaced in Europe by the cubic measurement of trees. The standing timber is valued according to the contents of its volume, as estimated in cubic feet. Estimates by cubic measure apply as well to the valuation of forests, as a whole, as to that of trees individually. The cubic quantity of timber and wood which can be taken out of a forest yearly, without causing any injury to the permanency of the supply, is ascertained as follows : — 1. The duration of the revolution of the forest has to be determined. (A forest has accomplished its revolution when the whole arboreal vegetation on it at the time it was taken in hand has been exhausted by successive annual fellings; so that, at the expiration of the revolution, the total area will consist of a regenerated forest, stocked with trees of various ages. The duration of the revolution is based on the age at which trees of the same species and in the same conditions of vegetation are considered to be ripe for the axe. Therefore, if the age at which trees are to be felled be one hundred years, the revolution would include a like number of years during which the forest must be worked yearly in such proportion as to afford about an equal quantity of the same produce for one hundred consecutive years * so pursuing the same system with new arboreal generations in perpetuity.) 2. The cubic volume of the ligneous material standing on the whole area has to be estimated, to which the computed future volume, or increment resulting from the growth of the trees up to the time they will come in turn to be felled, has to be added. 3. The total of the present and future volumes being then divided by the number of years comprised in the revolution, the quotient will show the quantity of produce that the forest is capable of supplying yearly for ever. Let Rbe revolution • V, present volume; a, the increment, or future volume ; A, the annual supply ■ then it will be— V+at A V + a — g- =A; ovA = — r -; This is the theory of the method generally adopted for the purpose of ascertaining the capability of forests as regards the annual supply derivable from them. The working of State forests is divided into several periods of the revolution, which come in rotation after exhaustion of all mature trees on the sections comprehended in the period. In practice, when the periods are of short duration—under twenty years, for instance—the experiments relative to the annual increase are generally neglected, and the estimates are only made upon the present volume. The latter mode of estimation is evidently the best adaptable to our native forests, where so many superannuated trees form the largest portion of the present volume of the forest. In the following table, the annual acreage, and the estimates in superficial feet, are taken in lieu of the cubic volume they are intended to represent. The estimates apply to a period of time—say, two years after formation of a special forest administration—when the New Zealand timber exports to Europe are supposed to be fairly started. Table I.

Extent of Forest Land, as required to supply annually and permanently the Demand for a Given Quantity.

* The fundamental conditions of a proper management of State forests consist —(1) in determining the quantity of the annual cuttings, so that about the same quantity may be obtained yearly and permanently; and (2) in operating, as regards the cuttings, in such manner or proportion that the natural regeneration of the forest should not thereby be impeded. Natural regeneration on the worked areas is secured by a judicious reservation of trees intended for seeding, and protection of the seedlings against prevailing winds. Plantations and transplantations on these extensive woodlands pre only resorted to as an exception to the general rule.

1. Total Area | of Valuable Forests in the hands of the Government, taken as 2. | Amount of the Demand (for Sawn Timber only), including Colonial Consumption and Exports, per annum, taken as 3. Average Yield of New Zealand Forests per Acre (for Sawn Timber only), taken as generally stated by Saw-millers. i 4. Annual Acreage of tho Fellings required to supply the Demand per Column 2. \ 5. Annual Acreage required to supply the Demand for Logs, Piles, Fencing Stuff, Shingles, and Firewood, taken as . 6. Total Annual Acreage required to supply the General Demand per Columns 4 and 5. 7. Total Area systematically required to allow the Acreage per Column 6. Tho Revolution taken as 125 Years. Acres. Superficial feet. Superficial feet. Acres. Acres. Acres. Acres. 5,000,000 300,000,000 15,000 20,000 20,000 40,000 5,000,000