Morphology, vegetation and development of Rokuanvaara, an esker and dune complex in Finland

Abstract

The area of study, Rokuanvaara, is situated to the north‑west of Oulu­järvi, Finland. A detailed survey is given of the landforms of the area, its history, vegetation and ground‑water table. This is based chiefly on observations made in the field and to a limited extent on aerial photo­graphs.

Rokuanvaara is an esker whose surface has been shaped by the action of wind, waves, run‑off water and earth flow. The upper part of the esker is covered by parabolic blow‑out dunes and the lower slopes by beach‑ ridge/dune complexes, while the surrounding lowlands are characterized by beach ridges, streamlets with deep valleys and ravines. The ground‑water table varies, being deeper on Rokuanvaara itself and nearer the surface in the surrounding area. The vegetation is composed of lichen‑rich forests and treeless heaths with peat bogs predominating in the adjacent lowlands. The principal factors in determining the vegetation pattern are the dry, sandy soil with a low nutrient content, the variable microclimatic conditions, forest fires and water percolating through the esker. The Boreal period was the most significant for the development of the landforms, while the Atlantic period saw the onset of paludification and a rise in the ground‑water table.