In the following I will show that it is not possible through pollen analysis to get an idea of the cultivation during the existence of the Celtic fields in general or to determine the start of the cultivation on the banks. The pollen so far found in the banks has to be dated to the Migration/Early Medieval period and it overshadows all traces of cultivation from earlier periods.
The discrepancy between the archaeological dating of the banks somewhere in the middle of the Iron Age and the high amount of Secale pollen can be explained either by tillage activities, mixing older and younger material, or by intrusion of younger pollen in older layers as result of percolation and bioturbation. Tillage activities cannot be excluded, but are dependent on the type of activity and its depth. As soon as the banks have reached a certain height and the spade or plough (ard?) no longer reaches into the lowermost layers the situation in these layers will be fossilized. This process must have taken place in the banks, otherwise the 14C dates and the OSL dates would have shown a rather mixed picture. This is not the case (Helt Nielsen 2009). The rate of downward movement of pollen is dependent on the type of soil and the soil fauna, reaching less deep in more acid soils (Stockmarr 1975, Groenman-van Waateringe 2012). After the formation of a humus podzol and an iron pan the downward movement stopped and the situation became frozen.
A dating of the rather high Secale values in the Early Medieval period, higher compared to the Roman period, but not as high as in the later plaggen soils, corresponds well with Behre’s idea of summer rye cultivation in the 1st millennium AD and is clearly shown in the pollen diagrams IV and VI from Flögeln (Behre and Kučan 1994). Considering the distance between the Celtic field of Flögeln-Haselhörn and these two pollen diagrams, c. 800-1000 m as the crow flies, the increase of cereal pollen from the Roman to the Migration period matches well with the Early Medieval data from the walls of the Celtic fields (cf. Behre & Kučan 1986, Table 1).
Zimmerman’s (1976) and Behre’s (2000) questions as to where to find the fields of the Late Roman/ Migration period (the settlement of Flögeln-Eekhöltjen (1st-5th c. AD) may now have received an answer. Mikkelsen (2003, 126) asks for more research concerning the supposed abandonment of the Celtic field system in the early Roman period, because in his view this is still an unanswered question.
Willy Groenman-van Waateringe
Revised submission: 12/3/2011