| Summary: | Little work has been done in Iceland regarding vegetation changes in peatlands in the context of soil chemical properties. This study examines interactions between climate, Histosols, vegetation and land use during the Holocene. Emphasis is on the development of cation exchange capacity (CEC), base saturation (BS), and decomposition rates using C:N and von Post humification. Soil physical properties were also determined. Vegetation development was reconstructed based on pollen analysis. In order to examine the impact of different geographic settings (coastal, inland and highland fringe), results from three sloping fens in Northwest Iceland were compared. Minerogenic soil content is highest in the proximity of the active volcanic belt, reflected in higher C:N values and greater ability to bind nutrients. The site closest to the sea reveals exceptionally high BS values. Overestimation of CEC due to oceanic precipitation may explain this pattern. Contrary to an expected decline of C:N with depth, values were stable or increased with depth. Evidently, C:N alone is not a reliable indicator of decomposition rates, but depends on the chemical composition of the organic parent material. The pollen record suggests optimal plant growth conditions at intermediate fertility levels. Differences in plant species richness between fertility levels are minor, but species diversity, species evenness and pollen concentrations are greatest at intermediate nutrient content. Environmental conditions driven by climate changes caused some changes in vegetation and soil properties before the settlement, but overall the Histosols showed resilience towards adverse impacts and severe degradation. After the settlement, they struggled to buffer the severe impact caused by destruction of vegetation and enhanced erosion. By connecting soil chemical and physical characteristics with palaeobotanical data, this study increases our understanding of environmental and anthropogenic determinants of soil- and vegetation development. ...
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