List of significant environmental and spatial predictor variables retained after a forward selection procedure in RDA models explaining the abundance of archaeological artefacts from each of the six considered time periods.

(+) and (–) designate positive and negative effects. respectively. The variables NEAR_SPRNG. NEAR_HILL and NEAR_RIVER i.e. the distance to the nearest river, hill or lake were included in models as distances. As a result the sign of the measured effect was inversed in order to be able to interpret these variables as proximities.