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Culture 2000

European Union

 

The Evidence from Pollen Analysis of a Bronze Age Mound in Bjäre, Sweden

by Jenny Nord Paulsson

The Bjäre peninsula

The Bjäre peninsula is situated in the north west of Skåne, the southernmost county of Sweden. About 14000 BC the ice of the last Ice Age began melting and this area was one of the first Scandinavian parts to be freed from the gigantic ice sheet. The enormous masses of ice had reshaped the area, giving the region a special appearance. In the north of the peninsula, some old rock “survived” the Ice Age and still rise up to heights around 200 meters above sea level. In all, the area hosts seven communities and measures about 200 km2.

The prehistoric heritage from Bjäre is very well preserved, consisting mainly of an unusually high density of Bronze Age graves and places with cup marks. More than 700 mounds from the Bronze Age are known. there are almost as many stone settings from the late Bronze Age and early Iron Age. Several hundreds sites with cup marks have also been noted. The larger carving sites also depict footprints and non-figurative carvings.





From the burial mounds we can gain insight into another kind of heritage from the past - the vegetation of their surroundings. An inventory has shown that the vegetation on the mounds of Bjäre is extremely well preserved from the times before artificial fertilisers were used. It is a flora typical for managed grassland. There are very few visible remains of earlier or later prehistoric date, and the prehistoric layers of visible remains of human activity in the landscape may therefore be summarised as a well-preserved ritual landscapes from the Bronze Age. Around these many soil layers of later farming landscapes have evolved.

The site of Bjäragården and Rishög

Situated in the very centre of the peninsula a 1,5 km long path offers a beautiful walk into the past at Bjäragården. The road used for hundreds of years for herding cattle (fägata) leads to Rishög, an impressive Bronze Age mound with a fantastic panorama vista across Skälderviken and Kullen, out to the island of Hallands Väderö and north towards Laholm Bay. At Bjäragården you will also find other remains from the past, e.g. graves from the Iron Age. Amongst them a stone circle (domarring), ancient rows of stones, cupmarks (skålgropar) and several other Bronze Age mounds (-hög) can be seen. One of these mounds is the legendary Elna Mårtens mound, in which trolls are said to have had their dwelling.



During the ECP project (European Cultural Paths) the Rishög mound was found to host well-preserved vegetation from times before artificial fertilizers. The idea was born to check whether the plants could possibly be a link back to the times when the mound was built. A small excavation took place in order to collect samples from the mound for pollen analysis.

 

 

Pollen analysis from the Bronze Age mound Rishög on the Bjäre-peninsula, Skåne, Sweden.

by Nils-Olov Svensson

Scientific background

Pollen analyses from different layers within archaeological features are considered to be connected to human activity. Archaeological features within layers are often caused by single events; the normal temporal continuity in the sequence of layering is missing or disturbed. The fact that layering is also influenced by the complex environment, makes the interpretation of archaeological features different and more complex than in landscape-connected studies in natural layers. In a grave mound built with surface material from the vicinity, most probably brought there as turf, the pollen content may give information about the local vegetation from where the turf once were taken.

The Rishög analysis

Three different layers could be distinguished in the mound;

the former ground level and underground (layer D)

the mound filling (layer B)

surface-earth (layer A).

The samples were collected from a small trench, which measured 3 x 0,5 meters. The samples were taken in the eastern part of the mound, closest to its centre. Here the trench was deepest, allowing collection of undisturbed mound filling.

 

Pollen analysis ( swedish abstract by Nils-Olof Svensson)

 

The pollen in the samples

Before the mound was built an original thin layer of soil had established itself above the rock. The pollen from this sample (layer D) had gathered at the soil surface and was partly transported down by water movements and animals e.g. worms before the mound was built. Pollen from Tilia (lime tree) is found in this layer. In the upper levels of layer D there are also remains of a rich, grazing meadow flora with high numbers of Plantago lanceolata (plantain), Poaceae (grass) and many herbs e.g. Campanula (bluebell), Ranunculaceae (buttercup family), Pimpinella saxifraga (burnet-saxifrage), Trifolium (clover), Rumex (dock sorrel) and Caryophyllaceae (carnation family). Caryophyllaceae are common through all layers, but only in layer D did we find a lot of Silene dioica (red and white campion). In layer D we also found quite a few spores from ferns, namely Polypodiaceae and Polypodium vulgare (polypody).

The transition to layer B shows a substantial decline of Tilia (lime tree) and a great increase in Poaceae (grass), which have very high spore numbers in layer B. The concentration of pollen also increases at the transition to layer B. The set of plants is slightly different than in layer D: Caryophyllaceae of the type Cerastium (chickweed) Ranunculaceae acris (meadow and tall buttercup) are common. Polypodiaceae (ferns) have decreased and are replaced by Bythrychium, Ophioglossum (Adder's-tongue ferns) and some Pteridium (bracken). Layer B, the building material of the mound, clearly originates from open grazing land with very few trees. The rich presence of charcoal shows that there had been burning activities in the area from where the material was taken. The variations in the concentration of pollen within layer B suggests that the material was dug up from different depths; nonetheless the high humus content from all samples shows that all material was collected relatively close to the surface soil. This proximity to the surface is also supported uniform appearance of the filling.

Layer B also contains a few Cerealia pollen spores (1 triticum type, 1 hordeum type, 4 cerealia type). However, they are so rare that it can be assumed that these crops did not occur in the vicinity. The lack of pollen from later immigrating trees and Secale (rye) together with low levels of lime tree spores show that the filling of the mound is from the late Subboreal period or the early Subatlanticum. It is difficult to get a closer dating since tree pollen is missing in the material. The mound filling can be dated to the Bronze or early Iron Age.

The top layer A contains higher humus levels than layer B and D. The sample, which was analysed, was taken 5 cm from the surface. Here pollen composition is dominated by Calluna (Heather). Juniperus (Juniper) is quite abundant as well, while grass and a lot of herbs show lower concentrations than in the other layers. There are also quite a lot of Lycopodium complanatum spores (Issler's Clubmoss). The relatively high amouns of heather are somewhat surprising since this plant is not common in the area today; the sample seems to represent the vegetation from slightly older period than today in spite of its closeness to the surface, a time when heather was abundant on the mound surface. But it is important to consider that the analysis only gives a local picture as one plant at the sampling spot would have been sufficient to produce a multitude of spores. The occurrence of Fagus (Beech), Carpinus (Hornbeam), Picea (Spruce) and Secale (rye), which are all late immigrants, shows that layer A is considerably younger than layer B.

 

The fossil/historic landscapes

Pre-mound (layer D): Before being used as a burial site, the sample area was previously a meadow with lime trees. Based on the pollen analysis, the flora directly at the burial site is somewhat different to the vegetation that grew in its surrounds. This may be because of the thin layer of soil here or the lack of a lime tree, which we assume, was only found directly on the burial mound. The occurrence of Polypody also suggests that the underlying rock was partly visible.

The filling (layer B): A general conclusion from the pollen analysis is that the mound's filling originates from very intensively grazed grassland. This is shown by the low frequency of tree pollen in combination with very high concentrations species, which are favoured by grazing. Hewever, nothing contradicts that the upper level of layer D and layer B are of the same age.

The surface (layer A): This layer represents the vegetation that has been growing on the mound since it was built. The sample holds evidence of heatherland, which no longer exists today, but might have dominated the area some hundred years ago.

Archaeological implications

The steady occurrence of Polygonum persicaria (lady thumb (eng), Floh-Knöterich (German)) in samples of layer B is noteworthy. Polygonum persicaria is an annual weed, common in crop fields, but also grows in humid areas as ditches and marches. However, it is not likely that Polygonum persicaria grew on the grazing land close by, which on the other hand is the most plausible origin for the filling of the mound. The inventory of today's flora on Bronze Age mounds on Bjäre (Gustafsson 1998) does not show any occurrences of Polygonum persicaria. One explanation might be that the plant has been able to establish itself as a flowering weed during the time when the mound was being built. The occurrence of the plant in all samples from layer B shows that the building of the mound was slow enough that Polygonum persicaria could continuously establish itself. This would suggest, that the mound was not completely built within one winter season.

 

References and proposals for further reading:

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Andersen, S. T.1996. Geobotaniske Undersøgelser af Kulturlandskabets Historie. Pollenanalyser fra gravhøje og søer i 1995. Udarbejdet for Skov- og Naturstyrelsen. Danmarks og Grønlands Geologiske undersøgelse. Rapport 1996/8. 55 sid.

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Berglund, B. E., Malmer, N. & Persson, T. 1991. Landscape-ecological aspects of long-term changes in the Ystad area. In: Berglund BE (ed) The cultural landscape during 6000 years in southern Sweden - the Ystad Project. Ecological Bulletins 41: 405424

Berglund, B. E. & Ralska-Jasiewiczowa, M. 1986. Pollen analysis and pollen diagrams. In: Berglund, B. E. (ed) Handbook of Holocene palaeoecology and palaeohydrology. Wiley, Chichester, pp 455-484

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