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The Vegetation of Tristan Da Cunha

N. M. Wace and M. W. Holdgate
Journal of Ecology
Vol. 46, No. 3 (Nov., 1958), pp. 593-620
DOI: 10.2307/2257541
Stable URL: http://www.jstor.org/stable/2257541
Page Count: 31
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The Vegetation of Tristan Da Cunha
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Abstract

Tristan da Cunha (37⚬ S., 12⚬ W.), a volcanic island of Tertiary age 12 km (8 miles) in diameter and 2060 m (6760 ft) high, has a temperate oceanic climate. The following vegetation types are recognized within the four main topographical units (Fig. 1): The Lowland Plains Strand and Blown-Sand communities Lowland Grassland Lowland Mires The Cliffs Scree and Rock-face Communities Blechnum penna-marina sward Phylica arborea bush and Blechnum palmiforme scrub Grassland The Base Phylica arborea bush Blechnum palmiforme scrub Empetrum rubrum heath Peat mires The Peak Rumex acetosella grassland Rhacomitrium-Empetrum heath Alpine desert Climatic change with altitude, and degree of slope and exposure are the main factors controlling the distribution of the community types below the Peak. Extreme exposure and instability of volcanic cinders are important factors above 1200 m (4000 ft). Human influence upon the vegetation, involving the conversion of lowland bush to grassland, the destruction of Phylica and tussock grasses, the establishment of Rumex acetosella grassland on the Peak, and the introduction of alien species are all discussed. The poverty of the flora and the high ecological amplitude of the few species on the island, leads to difficulties in comparing floristically the vegetation of Tristan with that of other areas, and in comparing different communities within the island. Physiognomic comparisons of the vegetation of Tristan with that of other volcanic mountains suggests a similarity to O Pico, and less marked resemblances to the tropical volcanic peaks of Hawaii, Mt Elgon and Fernando Po.

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