POPULATION STRATEGIES IN SEVERE ENVIRONMENTS - ALPINE PLANTS IN THE NORTHWESTERN CAUCASUS

This study attempts to show a differentiation into strategy types amon g plant species of four alpine communities in the northwestern Caucasu s, Russia. Four groups of population characteristics (traits) were exa mined: above-ground biomass, seed size, seed yield and occurrence of a persistent seed bank. In addition, values for relative growth rate an d a morphology index were estimated. Agglomerative Cluster Analysis an d Principal Component Analysis were applied to a data set with 42 spec ies from these communities and six species characteristics. In the Ger anium gymnocaulon meadow, the most productive community, large gaps oc cur created by wild boars and bears. Here, the response of 13 species to disturbance was also analysed. Strategy types were approached both according to Grime: 'competitive', 'ruderal', 'stress-tolerating' and according to Ramensky, Rabotnov and Romanovsky: 'violent' dominant (V) ,'explerent' explorative(E) and 'patient' endurant (P). Differentiatio n into strategy types was more obvious in productive alpine grasslands than in lichen heaths and snowbed communities. The grassland dominant s Festuca val-ia, Geranium gymnocaulon and Hedysarum caucasicum showed a more or less 'violent' strategy. Species approaching an E-strategy, e.g. Matrical ia caucasica, Sibbaldia procumbens and Gnaphalium supin um, were also found in the grasslands but prevailed in the snowbed com munities. Species with a 'patient' strategy prevailed in the lichen he aths. We conclude that plant strategy types are well-differentiated, t his is also seen in plant communities occurring under severe high-moun tain conditions. We also suggest that the approaches by Crime and Rame nsky/Rabotnov/Romanovsky are not so similar as has been assumed earlie r and that the R/R/R types are better differentiated and ecologically better interpretable. We emphasize the gradient character of strategy 'types' and would characterize plant species by the degree of adaptati on to conditions: (I) from small seed size and large persistent seed b ank to large seed size and absence of a seed bank; (2) from high to lo w biomass and seed production, with relative growth rate as a less imp ortant partially correlated trait.