Abstract
To determine whether modern pollen content in sediments from upland lake systems reflects the factual regional and extra-local vegetation composition, we analysed twenty-five samples focusing on aspects such as pond size and morphology, relative position in the catchment, local vegetation, canopy configuration and seasonality of the water table. The average pollen percentages of all sediment samples studied allows a fairly good reconstruction of the main vegetation units in the area, but major differences between the average samples obtained in each sedimentary system, and also between some samples taken from the same system are found. The main factors explaining those differences are the size of the pond, its tree canopy and the seasonality of the water table, which strongly determines the Ericaceae and Pinus percentages. A high-resolution multiproxy palaeoecological record from a small upland lake is re-evaluated in light of the new experimental evidence, and it is concluded that the interpretation of the importance of heathland and pinewoods in the Late Glacial landscape using pollen data may be magnified by the transport of both pollen types through water flows and their accumulation in the basin. Furthermore, anomalous Pinus pollen peaks occur in dry periods when the water table remains low. The sediment can also be depleted of some high-buoyancy pollen types (tetrads and saccate) when the water level is high and effluents are active. These effects may also be important in fluvio-marine systems in which Ericaceae and Pinus pollen are often overrepresented.
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