Estimating the spatial scale of pollen dispersal in the cultural landscape of southern Sweden

The primary aim of the study was to estimate the spatial scale of pollen dispersal and deposition for pollen assemblages from moss polsters in the cultivated landscape of southern Sweden, as a mean to improve future studies of the pollen/vegetation relationship in the region, and interpretation of fossil pollen data in terms of past cultural landscapes. This can be done by estimating the 'relevant source area of pollen' (RSAP) defined as the area around the pollen sampling point beyond which the pollen-vegetation relationship does not improve. Forty-two sites from nonfertilized grasslands in the traditional open agricultural (Open Region) and semi-open forested (Semi-Open Region) regions of southern Sweden were selected. The vegetation survey was performed within a 1500 m radius area around the moss polsters sampling area. The extended R-value (ERV) model was used to evaluate the pollen-plant abundance relationship. The RSAP for moss polsters in the Open Region was estimated to c. 400 m from empirical data. In the Semi-Open Region, however, the likelihood function score, an indicator of the goodness-of-fit of the data to the ERV model, showed an unexpected pattern of change, making it difficult to evaluate the RSAP. Simulations using hypothetical landscapes suggest that systematic selection of sampling sites could cause this pattern. Simulations also demonstrate that the size of vegetation patches affect the RSAP, i.e., the larger the vegetation patches are, the larger the RSAP becomes. Similar RSAP for the Open and Semi-Open Regions is obtained in simulations using the same patch size, and random selection. In the actual vegetation, patch size is comparable in the two regions, which would suggest that the RSAP for moss polsters in the Semi-Open Region is c. 400 m as well.