3 Palynological data from Celtic fields
There is ample evidence underneath the excavated Celtic fields in NW Europe for earlier pre-Celtic field arable activity Brongers 1976; Zimmermann 1976; Spek et al. 2003; Eriksen 2006). This can be in the form of ard traces underneath the walls or pollen data. However, in the pre-Celtic field period the amount of cereal pollen is extremely low, since the cereals grown were self-pollinating, producing low amounts of pollen which would not have been released in the air, and were only to be found in quantity where threshing took place.
This changes drastically in pollen samples taken from within the banks. The total amount of cereal pollen – part of which is clearly identified as Secale (rye) – has increased considerably, sometimes up to more than 20%, in relation to the numbers in the pre-Celtic field layers. In Vaassen (Casparie 1976) and Flögeln-Haselhörn the increase in cereal pollen can also be observed in layers interpreted as pre-Celtic field layers. How can this be explained, since the formation of the banks took place hundreds of years before rye was cultivated in NW Europe?
To solve this problem four sample series from Celtic field banks will be discussed in detail.
In 2001 samples for pollen analysis were taken from top to bottom in consecutive layers with distances of 2-5 cm from two banks and two fields in one section. In 2007 the same was done from two banks and one lynchet (2007/2) and from three fields in three different sections. Cereal pollen from underneath the banks was sparse. The banks themselves have high percentages (up to 20%) of cereal pollen, as far as identifiable, nearly all Secale. Values for Poaceae (grasses), Asteraceae liguliflorae (Composite family) and Spergula/Spergularia (spurry species) and for herbs in general are high.
In the samples from the fields and from the lynchet the amount of cereal grains is lower than in the samples from the banks in the strict sense.
Samples were taken as in Øster Lem Hede from a bank and field. Again the bank is characterized by rather high cereal percentages, partly identified as Secale (up to 10%, but total cereal percentages up to c. 20%). Values for Poaceae, Asteraceae. Spergula arvensis type, Chenopodiaceae (Goose-foot family), Polygonum persicaria type (lesser persicaria), Rumex-a type (sorrel) and Succisa pratensis (devil’s bit scabious) are high. The topmost samples of the field show the same high herb percentages. As stated “The combination of pollen types together with high values for Ericales strongly recalls the pollen assemblages of medieval plaggen soils” (Spek et al. 2003, 165). Also here are higher cereal values in the bank than in the field samples.
Behre & Kučan (1994) published four sections through Celtic field walls. In all four diagrams the percentages for Cerealia are high (with percentages of c. 28 and 34 in two of the samples, stratigraphically assigned to the pre-Celtic field phase. Not much can be said about the herbs, because the published diagrams are a selection of curves. The highest Cerealia percentages go together with rather high values for Succisa.
Pollen analysis in Vaassen comprises eight samples taken from various layers, spread over different parts of the excavation. Six samples belong to the pre-Celtic field phase. Cerealia were sparse. Only two samples (4 and 5) above each other in one of the banks – sample 4 from the old arable layer beneath the bank and 5 from within the bank – show slightly higher values for Cerealia, c. 5%. Casparie writes about these two samples: “From the very high percentages of Cerealia in spectra 4 and 5 it may be inferred that cereals, probably wheat, were grown here”. Spectra 7 (pre-Celtic field) and 8 (bank) have, according to Casparie, relatively many agriculture indicators, such as Plantago lanceolata (ribwort plantain), Rumex and Artemisisa (mugwort). Percentages for Poaceae, Polygonum persicaria and Asteraceae are specifically in sample 8 higher than in 7. He also mentions the presence of the hepatics Anthoceros laevis and A. punctatus (hornworts) (samples 4-5, 7-8).