Art. XLIX.—Effects of the Snowstorm of the 6th September, 1916, on the Vegetation of Stewart Island.
Communicated by Dr. Charles Chilton, C.M.Z.S.
[Read before the Philosophical Institute of Canterbury, 6th December, 1916, received by Editors, 30th December, 1916; issued ssparately, 10th December, 1917.]
On the 6th September, 1916, there occurred a particularly heavy snowstorm in Stewart Island, which caused considerable damage to many of the indigenous trees and shrubs, and the following particulars are perhaps worthy of being placed on record.
The weather of Stewart Island on the 6th September was very unusual. The first part of the day there was heavy rain for about seven hours, with little wind. About 10 p.m. the rain stopped, and a calm followed, with a dense fall of snow. The temperature was then about 50° F., and during the night it kept comparatively mild and warm, but towards dawn the sky cleared, and although still and absolutely calm it became bitterly cold. During this cold spell there could be heard, in the forest, trees and branches crashing down. As the sun appeared the sky again became cloudy, a light W.N.W. wind sprang up; the temperature rose to about 53° F., and the snow, which was about 5 m. deep, began to melt very fast—i.e., near the sea-coast and on beaches. By the evening about 2 in. of snow was left on the open land. The rainfall, including the snow, for the 6th was 3.68 in.
In the coastal scrub the tree most affected was Senecio rotundifolius; then, much less so, Dracophyllum longifolium, Coprosma spp., Nothopanax Colensoi, and large-sized manukas (Leptospermum scoparium var.). Olearia Colensoi, O. arborescens, and O. angustifolia do not appear to have suffered at all, nor the veronicas (V. elliptica, V salicifolia var. commums); but fuchsias (Fuchsia excorticata), although bare of leaves, suffered a good deal.
Of the trees and shrubs from other places planted on the section at my residence on Ulva Island, Senecio Huntii, Olearia Traversii, Coprosma robusta, C. grandifolia, and Arbutus unedo suffered badly, but the pines (Pinus radiata), larches, spruces, yew, &c., were not damaged at all. The six specimens of Brachyglottis repanda planted here, and now of large size, also escaped damage, a remarkable circumstance considering the great size of its leaves and its brittle twigs. In the forest the miro (Podocarpus ferrugineus) lost far the most branches, but few whole trees were down. Rimu (Dacrydium cupressinum) comes next. quite a number were uprooted, and branches were hanging from others in all directions Rata (Metrosideros lucida) and kamahi (Weinmannia racemosa) did not suffer so badly as the rimu, and totara (Podocarpus Hallii) seemed to stand the weight of snow fairly well; but a number of all the larger trees in the forest on Ulva were uprooted. In some instances flood-water covered the ground around their roots. The cabbage-tree (Cordyline australis) had all the outside leaves bent down; but this will not matter, as new leaves will soon form.
The Government tracks on Ulva are now cleared, and I got one of the men to help me on the section. We removed nearly a cord of firewood from branches on the tracks within a radius of about 5 chains, and this should give an idea of the average fall of branches, whole trees being omitted.
The old Natives here say there is no record among them of such damage to the trees by snow as the present one. I may mention that a few days before the snowstorm thousands of kakas and pigeons arrived at Ulva, and many are still here.