Quantification of past plant abundances based on the R-value model: Exemplified by an impact assessment of pre-historic iron production and summer farming in Budalen,central Norway

Abstract

Quantification of vegetation cover based on fossil pollen assemblages is valuable for proper assessment of past landscape dynamics. In the present investigation, the past vegetation cover around a pre-historic iron production site in the Budalen valley in central Norway was quantified using direction of vegetation change models. A set of fixed rules based on normal succession, the present vegetation and the ‘intuitively’ interpreted fossil pollen record was used to model spatially explicit changes in the vegetation of past landscapes. By comparing modelled pollen percentages with empirical fossil pollen percentages, it was possible to determine absolute plausible vegetation. According to the applied models, the pine forest within at least 1 km of the sampling site (>100 ha) was temporarily replaced with birch forest around ad 300, 800 and 1750 as a consequence of iron and charcoal production. The birch forest later re-succeeded to pine forest as pine harvest decreased at intermediate time stages.