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8. Note by the Inspector-General of Forests to the Governinent of India on the Growth of Pinus Massoniana in the Island of Hongkong.
The conditions are as follows:-There are about 5,000 acres of plantation of Pinus massoniana costing in creation about $35 per acre and in annual up-keep $1,738 in establishment and (say) $500 for protection. The local rate of interest is 6 per cent.
The best rotation from an economical point of view is required.
2. Measurements of 4 trees are given. This is insufficient save as a slight guide for an expression of opinion affecting a large area, but taking these measurements as typical and the other statements as accurate for the whole locality we find –
(a.) That 35 feet is considered to be a good height growth and that this
is attained in about 20 to 30 years.
(b.) That the trees attain a comparatively large girth but that the girth
increment falls off at about 30 years of age.
From an economical point of view therefore it is evident that it would be preferable to fell the trees after they have attained their full height growth and as soon as the girth increment shows signs of falling off if the outturn is to be utilised solely as fuel. At 30 years of age the 4 trees measured show a diameter of 28.2 inches, of 12.2 inches, of 18.4 inches and 16.8 inches. The first tree is certainly not typical of the whole area and the others would not yield any quantity of planking. At 50 years of age the 3 last stems show a diameter of 15.6 inches, of 22.8 inches, of 20.4 inches. That is they have increased in 20 years only by 3.4 inches, by 4.4 inches and by 3.6 inches in diameter. Still they are not large enough to justify their retention for a term of 20 years at the high rate of interest in force.
3. I should say that the period of the average felling rotation might well be fixed at 30 years, with another 5 years allowed in exceptional conditions after investigations made on the spot (by means of a borer) to prove that there is no falling off in the annual increment. The felling of the trees at 30 to 35 years would not affect the beauty of the sylvan scenery. They would to the ordinary observer be as large then as they would be 20 years later though possibly more free from the picturesque contortions of disease and age.
4. But the extremely low height-growth and vitality shown in the above statistics points to the absence of suitable nutriment and protection of the soil. Fires are common and there is little humus; that under the trees is collected by natives who derive their living from unauthorised removals. If protection were adequate the height and girth growth would rapidly increase. I consider that for $1 it should be easy to protect 10 acres of plantation from fire and that it would be cheaper to provide for the poor Chinese in cash than in kind, when that kind consists of the life nutriment of the forest.
5. I see Hongkong is about 22° North latitude, with an average mean temperature of 71.5° and a mean rainfall of 8.69′′ distributed over every month of the year, but in no month excessive. I would be glad to supply seed of Pinus longifolia and Pinus Khasya for trial if these have not been before attempted. It is a question for consideration whether the fellings of the existing crop should not be carried out by selection of the mature stems, the blanks caused by removal being sown or planted up so to avoid the occurrence of blank unsightly areas which must result from clear fellings. If sowings were resorted to a much denser crop than 1,000 to the acre could be assured at a cheaper rate and to the better protection of the soil. Perhaps there are local reasons forbidding this, but in any case the forest to be beautiful and valuable must be protected from fire and not robbed of nature's nutriment.
9. Decision of His Excellency the Governor in Council.
The above correspondence was laid before the Executive Council by command of His Excellency the Governor, and at a Meeting held on the 24th July, 1905, it was recommended that a thirty-five years' rotation should be adopted, subject to special permission being given for felling young trees on proof of falling off in annual increment, and that "selection" felling should be substituted for "block" felling except in the areas in the neighbourhood of Tytam and Stanley known as Forest Districts 4 and 5.