Distribution of Raunkiær’s life-forms along altitudinal gradients in the Faroe Islands

Abstract

Úrtak Fyri at vita, hvar vøksturin í Føroyum skiftir frá at vera arktiskur til at vera tempereraður, kannaðu vit útbreiðsluna av lívshættum Raunkiærs niðan eftir fimm ymiskum fjalla síðum. Eisini kannaðu vit, hvønn týdning gróðrarlag ið, LOI (gløðitap) og árligur miðalhiti hava fyri útbreiðsluna av lívshættum við hæddini. Okkara niðurstøða var, at tíðleikin av hemikryptofytum minkaði linjurætt við hæddini, tíðleikin av therofytum og geofytum vaks linjurætt við hæddini, og rásin, sum vísir tíðleikanav charmaifytum sum funktión av hæddini hevur skap sum parabil, við lægsta tíðleikanum á 400-500 m hædd.Tíðleikin av hemikryptofytum samsvarar eins væl við lága gróðrarlagið sum við hæddina, men thero fytarnir samsvara best við lága gróðrarlagið. Chamae fytarnir samsvara best við tann árliga miðal hitan, men geo fytarnir samsvara best við LOI. Kanningin vísir, at lutfallið millum hemikryptofytar og cham ae fytar broytist við hæddini, sum vøksturin skiftir frá tempereraðum til arktiskt eyðkenni. Abstract To study the shift from temperate to arctic vegetation in the Faroe Islands, we quantitatively analysed the distribution of Raunkiær’s life-forms along five altitudinal gradients. We further tested the importance of the non-climatic parameters of altitude, total vegetation cover and LOI (loss on ignition), and the climate variable of annual mean temperature in describing the abundance variation of life-forms. We found that as altitude increased, the abundance of hemicryptophytes decreased linearly; the abundance of therophytes and geophytes increased linearly; and the abundance of chamaephytes varied parabolically, with the lowest abundance around 400-500 m. The abundance variation of hemicryptophytes seems to be as wellcorrelated with total vegetation cover as with altitude, while total vegetation cover was the best parameter to describe the variation in abundance of therophytes. Annual mean temperature was the most important parameter for describing the abundance variation of chamaephytes and LOI was the most important parameter describing the variation of geophytes. Weconcluded that the abundance rela tionship between hemicryptophytes and chamae phytes changed with altitude as the vegetation changed from temperate to arctic vegetation.