Åsgraven

The depression was created by a large block of ice that remained for a long time during the melting of the ice and prevented the deposition of gravel and sand. Gradually, a small gully was formed in the depression, first depositing clayey sand and then various types of mud and peat, while the gully was ground up into a marsh. These organic deposits are about two meters thick and contain the remains of reeds, mosses, twigs and leaves as well as seeds of e.g. water clover, but above all pollen from various plants on the site and from the entire surrounding area. By analyzing the pollen composition in different layers, it has been possible to follow the development of vegetation over 10,000 years (Esplund Lindquist 1993).

When the area became ice-free, there was a period of grass tundra, which after a couple of thousand years changed to grassland with elements of birch and pine and later also alder and hazel. This was followed by a period of several degrees warmer climate, when lush oak mixed forest with elm and lime spread. It is known that during this warm period between 5,000 and 8,000 years ago, the bog turtle was present in these areas. Then it became colder again, and elm declined, birch increased and beech migrated in from the south. Spruce, on the other hand, came from the north and began to migrate 2 000 years ago.