Pollen analysis of soil samples from the A.D. 79 level. Boscoreale, Oplontis, and Pompeii

Fifty samples of Roman time soil preserved under the thick ash layer of the A.D.79 eruption of Mt Vesuvius were studied by pollen analysis: 33 samples from a former vineyard surrounding a Villa Rustica at Boscoreale (excavation site 40 x 50 m), 13 samples taken along the 60 m long swimming pool in the sculpture garden of the Villa of Poppaea at Oplontis, and four samples from the formal garden (12.4 x 17.5 m) of the House of the Gold Bracelet in Pompeii. To avoid contamination with modern pollen all samples were taken immediately after uncovering a new portion of the A.D. 79 soil. For comparison also samples of modern Italian soils were studied. Using standard methods for pollen preparation the pollen content of 15 of the archaeological samples proved to be too little to reach a pollen sum of more than 100 grains. The pollen spectra of these samples are not shown in the pollen tables. (Flotation with a sodium tungstate solution, Na2WO4, D = 2.05, following treatment with HCl and NaOH would probably have given a somewhat better result. This method was, however, not available as too expensive at that time.) Although the archaeological samples were taken a few meters apart their pollen values differ very much from one sample to the other. E.g., at Boscoreale (SW quarter). the pollen values of Pinus range from 1.5 to 54.5% resp. from 1 to 244 pine pollen grains per 1 gram of soil, the extremes even found under pine trees. Vitis pollen was present in 7 of the 11 vineyard samples from Boscoreale (NE quarter) only. Although a maximum of 21.7% is reached, the values of Vitis are mostly below 1.5%. Even the values of common weeds differ very much, not only at Boscoreale, but also at the other two sites. The pollen concentration values show similar variations: 3 to 3053 grains and spores were found in 1 g of soil. The mean value (290) is much less than the number of pollen grains, which would fall on 1 cm2 of soil surface during one year. In contrast, the pollen and spore concentrations of the recent soil samples, treated in exactly the same manner, range from 9313 to almost 80000 grains per 1 g of soil. Evidently most of the Roman time pollen has disappeared since its deposition, the reasons not being clear. Not even species which are known to have been cultivated in the garden of Oplontis, like Citrus and Nerium, plant species with easily distinguishable pollen grains, could be traced by pollen analysis. The loss of most of the pollen grains originally contained in the soil prohibits any detailed interpretation of the Pompeian pollen data. The pollen counts merely name plant species which grew in the region, but not necessarily on the excavated plots.