Pollen Analysis :: essays research papers

The remains of ancient plants can provide a wealth of archaeological information about a site, with many methods being available to the archaeologist engaged in extracting this data. Perhaps one of the most widely-known of these techniques, possibly because of its attractive nature, is pollen analysis - a technique developed in the early years of the twentieth century by, like so many archaeological techniques, a geologist -- the Norwegian Lennart van Post. To understand the technique and the uses to which it may be put, we must first examine the biological nature of the material itself. Because of a hard outer shell - the exine - pollen is particularly resistant to chemical attack and will survive in most conditions; the only environments which are truly hostile to this shell are abrasion, such as may be the case on sandy sites, and oxidation. However, the most favourable conditions for preservation of the pollen record are acidic, anaerobic sites such as peat bogs. This high degree of survivability combines with another factor inherent in the nature of pollen - the large amount produced - to make pollen analysis one of the most important tools available to the archaeologist. Though one further factor in the make-up of pollen enhances its value, namely the wide morphological variation between pollen from different plant species, most of which can be detected and classified using normal laboratory equipment. Pollen analysis is a technique which demands a high level of skill on the part of the excavator, scientist and interpreter to enable it to fulfil its potential. Collection of pollen samples can prove troublesome, the risk of cross-contamination is significant and efforts must be made to minimize the effect of any excavational bias. The number and ratio of pollen grains present in a sample can also be skewed by factors such as the orientation of the site and the nature of the pollen grains themselves, for example, trees such as pine produce much greater quantities of pollen than species such as oak and thus have a tendency to overrepresent themselves in the pollen record. Once collected the pollen is extracted from the soil, usually in the laboratory to avoid contamination, and analysed using a light, or scanning electron microscope (SEM). The wide differentiation in the size, shape and colour of the pollen grains enables identification to be made down to genera level. Following identification, the individual exines in a sub-set of the sample are quantified and plotted on a pollen analysis diagram, usually as a percentage of the whole.