Using models of pollen dispersal and deposition in hilly landscapes: Some possible approaches

Recent developments in the modelling of pollen dispersal and deposition have led to the development of user-friendly computer software for simulating vegetation mosaics and pollen assemblages at specified points within those mosaics. In this paper we discuss the possible application of these approaches to modelling the pollen deposition in mountain areas. First, we demonstrate the use of the Multiple Scenario Approach by reconstructing mid-Holocene tree line position in the southern Dark Peak area of the Peak District in northern England from a published pollen record. However, the underlying model of pollen dispersal and deposition assumes a flat landscape, which makes extending the approach to mountainous areas problematic. Therefore we also present simulation experiments exploring the effects of modifying aspects of the existing model to better simulate the montane situation (ecotone structure, changes in the wind rose to mimic the effects of topography on aerial pollen transport). We suggest that, as a first approximation, topographic effects can be incorporated in the models by varying the wind rose at the sampling point to reflect the impact of topography on air flow.