BASALTIC SOILS OF SOUTH‐WEST ICELAND. I

Abstract

SummaryA preselected grid of sixty‐five randomly arranged sampling sites was the basis for a preliminary soil survey in south‐west Iceland.The soils were divided into freely drained soils and poorly drained soils, the larger group being freely drained, of which many were shallow lithosols and regosols varying in depth from a few cm. to 1–2 m.Visible soil characteristics result mainly from physical effects of climate and recent age of the soil parent material. The combined processes of alternate freeze and thaw and wind deposition have disrupted orderly soil morphology. Colour differences, usually varying shades of brown, are therefore minimized, and the mineral matter shows little sign of horizon differentiation, apart from bands of wind‐deposited volcanic ash. The poorly drained soils are mucky in appearance with a non‐indurated layer of bog iron above the permanent water‐table. Waterlogged conditions do not always lead to general gleying.Under the prevailing sub‐arctic climatic conditions grasses and most other species are shallow‐rooted, forming a surface mat 5–7 cm. thick.Field texture of freely drained surface soils is usually loamy, but may be extensively conditioned by high organic matter contents. Structure is weak platy, changing to block‐like and/or to single‐grained structure. On drying, soil aggregates usually disintegrate at the least pressure applied.Many surface features, normally related to frost action, occur, including earth hummocks, scars, V‐shaped gullies, polygons, and stone stripes. Perma‐frost is absent.