Sammendrag
To determine the effect of macroclimate and habitat on leaf characters, the length and shape of stem and branch leaves of Sphagnum strictum from herbarium specimens covering all parts of the species distribution in Norway, were obsrerved and measured. The measurements were related to interpolated macroclimatic data by stepwise multiple regression. Similar measurements on branch leaves were obtained from 71 plots of S. strictum at eight localities, and the morphological data were related to vegetation data from the plots. A shift from short branch leaves which are narrow above towards long and broad ones was observed along a regional gradient from south and southwest and lowland sites, towards north and subalpine ones. This shift in morphology was also observed along the vegetational gradient: pine woodland - heath - mire fen hummock - mire fen lawn. Both studies support the hypothesis that short branch leaves with an involute portion above might have an adaptive significance in retaining water of Sphagnum strictum living in fairly dry habitats with warm summers, and where capillary movement of subsoil water can be difficult.
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