Regional variation in SE Fennoscandian mire vegetation.

Abstract

The distribution in bogs is outlined for all species occurring in bogs only in part of their SE Fennoscandian area. The patterns displayed by these species are diverse, and different explanations are applicable to different patterns. Regional variation in SE Fennoscandian bog and extremely poor fen vegetation is described, based on all available published material. Carpets, lawns, and hummocks are considered separately. Four regional vegetational gradients are identified: (1) W‐E, (2) S‐N, (3) SW‐NE, and (4) NW‐SE. These are related to different underlying climatic gradients: (1) humidity (precipitation surplus), (2) temperature, (3) and (4) combinations of humidity and temperature. Effects of climatic gradients on the ground water regime are outlined. The decisive factor for the SW‐NE gradient is probably frequency of ground water table fluctuations, the NW‐SE gradient is likely to be caused by differences in water supply and ground water flow rates. The main gradient of carpets is S‐N (SE‐NW), of lawns SW‐NE (W‐E), and of hummocks partly SW‐NE, partly S‐N. The effects of the underlying ecological factors on the different plant groups are discussed in order to explain the patterns of regional variation in vegetation.