Vegetation and Soils in the South Chilean Islands

South-western Chile, between 42⚬S. and 56⚬S., is a region of mountainous islands with an oceanic climate and evergreen rain-forest or peat-forming herbaceous vegetation. At Chepu on Chiloe Island (42⚬S.) much of the country is made up of alternating ridges and hollows. The former support a rich broad-leaved evergreen forest (Valdivian forest) dominated by Eucryphia cordifolia, Weinmannia trichosperma, Laurelia serrata and Amomyrtus spp. These areas have a brown-earth soil whose upper layers contain about 36% organic matter (expressed as a percentage of dry weight) and have a mean pH of 4.9. The hollows contain woodland dominated by Nothofagus nitida and Tepualia stipularis: they have waterlogged peaty soils of about 60% organic content and pH 3.8 to 4.0. This separation of the two vegetation types is of interest because the Eucryphia forest is characteristic of warmer and drier regions ranging northwards from the study area while Nothofagus woodlands characterize the colder and rainier southern regions. On the central uplands of Chiloe Island peat formation still occurs chiefly in hollows, and Astelia pumila dominates the bog vegetation. Gleys and peaty gleys are widespread, and the forest patches (of Nothofagus) have only shallow superficial acid (mor) humus layers. Farther south, at Puerto Eden on Wellington Island (49⚬S.), while the vegetation has much in common with the Chiloe uplands, blanket peat is developed almost everywhere below 600 m, and this is certainly to be associated with the much higher rainfall. Peats developed in Nothofagus forest, Tepualia patches and heath, and Astelia-Donatia bog have alike between 90 and 96% organic content, and pH from 3.7 to 3.9. Only on the mountains above 600 m is peat formation checked and an appreciable amount of wind-blown mineral matter incorporated in the material below the vegetation mats. In contrast to these wet western areas, the northern shores of Navarino Island (55⚬S.) have a rainfall below 20 in. (51 cm) and a vegetation of deciduous woodland developed over very dry, free-draining brown earth soils derived from a parent material of moraine and glacial sands. Peat formation is here restricted to regions of impeded drainage, and even on the uplands organic accumulations only occur in streamside bogs and within cushions of plants such as Bolax and Azorella species.