The use of pollen analysis to reveal Holocene treeline dynamics: a modelling approach

Abstract

This paper presents the results of simulated pollen counts from the central Scandes Mountains in Sweden which are used to examine the application of a pollen-based modelling approach to treeline fluctuations. Treelines are considered sensitive indicators of climate variability, and greater consideration of the palynological signal of treeline fluctuations is important in critical and rigorous use of pollen analysis to reconstruct variations in treelines. The approach presented here is to construct GIS-based models of the landscape (based on topographic and land cover attributes) onto which placement of different vegetation communities can represent changes in treelines in space (by adjusting the altitudinal positioning of treelines) and time (by using five time slices through the Holocene). The application of the POLLSCAPE model of pollen dispersal and deposition is then applied to generate simulated pollen counts for a large number (121) of sites placed across an altitudinal range in the simulated landscape. Comparison of simulated data to empirical pollen data from the region validates the approach through reasonable matching of the main trends in the pollen data sets. The success of the modelling approach is that it has helped to refine the process by which variations in fossil pollen assemblages are constructed, and also provides a tool by which the optimum sampling locations can be determined for treeline-focused work.