EXOTICS IN BUSH

Evening Post, Volume CV, Issue 127, 31 May 1928, Page 7

EXOTICS IN BUSH

EXPERIMENT NEEDED N.Z. BEECH REGENERATION NATIVE OR FOREIGN ? The possibility of profitably growing exotic trees within the indegenous forest of New Zealand lias from time to time been touched on; and it is .interesting to note that the idea is tentatively considered, so far as beech forests are concerned, by Dr. L. Cockayne, who, in a report to the Forest Service on beech forests, suggests that certain experiments should bo made at no great cost. However, his. present impression is that pure beech forests will pay best as self-regenerating P m'o beech forests, because of their'power to re.generate naturally "without involving any outlay whatsoever" (although it may be .found that thinning" and other silvieullural methods wilt increase the return), and because ihey do so "on ground so poor that its rental value ia almost negligible." - He offers the opinion that "it will not be easy to find any other tree to take 'the place of the beeches which will yield timber, of similar value, nor are equally good and faster-growing exotics likely to thrive on all classes of soil, at low or high altitudes, as the case may be, or produce anything like the same yield. Nor does it seem likely that tho regenerating power of the exotics would equal, or continue so long as in the case of the beeches. At tho same time, I may be wrong, and so certain cheap experiments are suggested regarding Die growing of exotic trees wjthin the beech forest, which should shed considerable light on this fundamental matter." EXOTICS TO FILL GAPS? Later in his report Dr. Cockayne states that ;i fault of natural regeneration "is the almost certain occurrence of gaps hero and there where there arc no voting beeches. AVcro bcoch nuts readily procurable.in quantity—and in certain forests during seasons of heavy blooming this should bo possible—actual sowing could bo resorted to. The seed would need to bo sown immediately after collecting; no seed should be kept over from one season to the next. This matter of procuring seed in quantity requires investigation. Evidently there is no' constancy in the yearly yield of seed—some years it is in profusion, but in pther years there is very little. Gaps where seedling or sapling beeches were wanting could, of course, bo filled by planting young trees. The question at unco arises should beeches or exotic trees be made use of1? The latter possibly would be the better, for it would be easier to procure plants which would become established without much loss than in the ease of the beech, and species yielding a. better timber would increase' the value of the forest. Oregon pine (Pseudotsuga taxifolia) at once suggests itself for tho majority of localities.- It is growing excellently in tho municipal foresty plantations of Duncdin on land formerly carrying rain--I'orest proper under a climate similar to that of many beech forests. Chamaceyparis Lawsoniana, Thuya plicata, and T. gigantea might also be suitable. Tho first-named grows splendidly at Beefton in former beech-forest soil. An objection to introducing exotic trees is that thoy would most likely bo ready | for cutting before the beech; but in the case of tho above, though early cutting | might pay best were they in great quan-1 tity, delay would lead to considerable increase in yield. frequently, howover, the beeches themselves would be of uneven age, and tho forest would mature unevenly, so that it would bo cut over at different periods, and the exotics would come in along with the earlier maturing beeches for the first crop. Sowing the seeds of exotics in situ would bo much cheaper than planting; but experiment, as discussed farther on under another head, should be a preliminary." EXPERIMENTING METHOD. Under the heading of "experiments," Dr. Cockayne reports that "nothing is known, or at any rate put on record, regarding .the sowing of seeds of exotic trees in situ within the forest, or on the ground left bare after milling has taken' place. Hero experiment is urgently demanded, and there is no need that such bo either elaborate or expensive; indeed, much can bo done by the rangers without interfering to any marked degree with their ordinary duties. Quite small areas would, in tho first instance, be sufficient. There is nearly always a dcsiro to carry out experiments on a largo scale, though small areas can be examined with greater care^and the results rapidly appraised. Tho seed should in one class of experiment be merely cast upon the ground, and the area bo perhaps only a few squaro yards. As in my experiments for the Department of Agriculture, designed to find out the principles upon which, were it possible, depleted Central Otago could be regrassed, a mixture of the seeds of different species was used. So in lilte manner a mixture of seeds of different trees could be employed. This plan saves much time and space, and once the seedlings of each species are .known the various speei J cjiii be watched just as well as if each were by itself. Also, their relative .-ates of growth, and. other matters of their behaviour, can be learnt with certainty. Suelfan experiment is not for the purpose of attempting reafforestation, but to observe merely what happens, which species germinate and which, do not, tlie relative rates of growth, whether the bare humus, the bryophyte carpet, or the floor covered with beech-leaves—to cite a few seedbeds—best favours germination, and other.matters. Tor sowing within the forest interior shade-tolerating species are necessary. Now, it is not easy to got defmito information on this head, ltecords from European forestry concorn in great part those species which thrive only under the canopy of deciduous trees, such as Ihc larch. AVhat are wanted here arc species which can grow, as do those of Ndthofagus, under tho roof-canopy of ordinary beech forest. . . . AVhore forest has been milled or burned, experiments should bo made with light-demanding species." After giving a list of species which he recommends for experimental sowing, Dr. Cockayne: writes: "There is not the slightest reason why apparently unlikely species should not be tested; it is experiment, not demonstration, that is proposed. .'■ . It must not be forgotten that no experiment, properly conducted, can fail j negative or positive results arc equally successes."