Climate envelopes of mire complex types in Fennoscandia

Peatlands are characteristic features of the Fennoscandian landscape, about one-quarter of the land surface being classified as peatland. The aim of this work was to determine the extent to which the distribution of four main mire complex types (aapa mire, blanket bog, palsa mire, raised bog) can be modelled on the basis of climatological parameters. Additionally, the relative importance of different climatological variables in influencing the distribution of different mire complex types was scrutinized using the variation partitioning method. Variation partitioning is a novel statistical approach that provides deeper understanding of the importance of different explanatory variable groups for geographical patterns than traditional regression methods. The variation in the distribution of mire complex types was decomposed into independent and joint effects of temperature, precipitation and spatial variables. The distributional limits of aapa mires, palsa mires and raised bogs were primarily associated with thermal factors, whereas moisture regime also played an obvious role for blanket bogs. A considerable amount of variation in the distribution of mire complex types was accounted for by the joint effects of explanatory variables and may thus be causally related to two or all three groups of variables. Although the present distribution of mire complex types corresponded well to the contemporary climate in Fennoscandia, our results indicate that the climate envelopes of palsa mires are narrow. Thus, they can be expected to be extremely sensitive to changes in future climatic conditions.