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Absolute Pollen Frequency
CATEGORY: measure
DEFINITION: A pollen density measure in which pollen counts per unit volume of sediment are corrected by estimated deposition rate (depth per year) to estimated influx (counts per cm per year), the same unit used for pollen rain in modern samples. Each taxon varies independently of the others making interpretation much easier than with percentages.
absolute pollen counting
CATEGORY: technique
DEFINITION: Absolute pollen counting is the determination of the number of grains of each pollen type per unit weight (grains/gram) or unit volume (grains/cm3) of sample. Variation in the rate of sedimentation sometimes makes the number of years represented uncertain; absolute counts for different samples may therefore not be compatible. Pollen analysis is then calibrated with radiocarbon dating to create pollen influx rates figured by the number of grains of each pollen type accumulating on a unit area of lake or bog surface in one year (grains/cm2/year) for each sample.
arboreal pollen
DEFINITION: Pollen from trees.
nonarboreal pollen
DEFINITION: Pollen from nontree plants, such as sedges and grasses.
DEFINITION: Plant sperm or armored gametophytes. Pollen's outermost layer, the exine, survives in archaeological context.
pollen analysis
CATEGORY: technique
DEFINITION: The study of pollen grains in soil samples from an archaeological site which provides information on ancient human use of plants and plant resources. This technique, which is used in establishing relative chronologies as well as in environmental archaeology, was developed primarily as a technique for the relative dating of natural horizons. Pollen grains are produced in vast quantities by all plants, especially the wind-pollinated tree species. The outer skin (exine) of these grains is remarkably resistant to decay, and on wet ground or on a buried surface, it will be preserved, locked in the humus content. The pollen grains of trees, shrubs, grasses, and flowers are preserved in either anaerobic conditions or in acid soils. Samples can be taken from the deposits by means of a core or from individual layers at frequent intervals in a section face on an archaeological site. The pollen is extracted and then concentrated and stained and examined under a microscope. Pollen grains are identifiable by their shape, and the percentages of the different species present in each sample are recorded on a pollen diagram. A comparison of the pollen diagrams for different levels within a deposit allows the identification of changes in the percentages of species and thus changes in the environment. As a dating technique, pollen has been used to identify different zones of arboreal vegetation which often correspond to climatic changes. The technique is invaluable for disclosing the environment of early man's sites and can even, over and series of samples, reveal man's influence on his environment by, for example, forest clearance. The sediments most frequently investigated are peat and lake deposits, but the more acid soils, such as podsols, are also analyzed. Radiocarbon dates may be taken at intervals in the sequence, and it is possible to reconstruct the history of vegetation in the area around the site where the samples were taken. Palynology plays an important role in the investigation of ancient climates, particularly through studies of deposits formed during glacial and interglacial stages of the Pleistocene epoch.
pollen core
CATEGORY: technique
DEFINITION: A stratified sample of soil or sediment that is taken to recover the plant pollen, and hence to discover changes in the local vegetation over time. A column of soil or peat is extracted from the ground containing a continuous record of pollen grains representative of changing vegetation over a period of time - and the deeper the core, the older the pollen.
pollen dating
CATEGORY: technique
DEFINITION: Using local pollen sequences to provide a relative date for a site.
pollen diagram
CATEGORY: technique
DEFINITION: A diagram produced after the analysis of the pollen from a column of peat or other soil. Pollen diagrams consist of a number of graphs, showing the fluctuations of different pollen types through a sediment or soil. The vertical axis of the diagram represents depth through the deposit and is therefore roughly related to time, as the deeper layers are the oldest. Each small graph represents the changing frequency of one pollen type, either as a percentage (proportional pollen counting) or as an absolute frequency (absolute pollen counting). It is often possible to split the diagram up into a number of pollen zones, each dominated by high frequencies of a particular pollen type or types.
pollen influx
CATEGORY: technique
DEFINITION: An estimate of the number of pollen grains incorporated into a fixed volume of sediments over a particular time. If the pollen influx is known, the number of years contained in a certain volume of sediment can be estimated.
pollen zone
CATEGORY: technique
DEFINITION: A division that can be drawn across a pollen diagram on the basis of fluctuations in pollen types. Each pollen zone is dominated by high frequencies of a particular pollen type or types. In recent years, many palynologists have abandoned general zonation schemes and instead have divided their pollen diagrams into 'pollen assemblage zones' (p.a.z.). These are based simply on the pollen fluctuations seen in each particular diagram and can therefore take account of local variation in the history of vegetation.
proportional pollen counting
CATEGORY: technique
DEFINITION: A type of pollen analysis carried out by determining the proportion of different pollen types in each sample. Proportions are usually expressed as percentages of total tree (arboreal) pollen. This method is fairly quick as only a fraction of the grains present in a sample need be counted. Its main disadvantage is that percentages can never indicate actual numbers of grains falling to earth, which is solved by Absolute Pollen Counting.

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