Growth Studies of Selected Plant Species with Well-Defined European Distributions: I. Field Observations and Computer Simulations on Plant Life Cycles at Two Altitudes

Abstract

(1) Field observations on the life cycles of species with continental, oceanic, montane and arctic-alpine patterns of distribution have demonstrated that low winter survival prevents the establishment of Digitalis purpurea (oceanic) and Eupatorium cannabinum (continental), at altitudes above their present limits. (2) Computer simulations of population densities have predicted that Potentilla reptans (continental) should also become extinct, after a longer period of time at the same altitude. In this case, failure to extend the altitudinal range is a result of the combined influences of low seed germination, winter survival and seed production. (3) Observations of germination, plant survival and seed production in the arcticalpine species, Oxyria digyna and Saxifraga stellaris provided no clue to their absence from the Welsh lowlands. Both species demonstrated and were predicted to show continued and successful population survival. Slow leaf area expansion resulting in low competitive ability is likely to be the key to their restriction.