Establishment, survival and dispersal limitations of pioneer plants in a Norwegian glacier foreland as revealed by seed sowing, transplantation and seed bank experiments

• Main Author: Strømme, Anne-Sofie Bergene
• Other Authors: Ohlson, Mikael
• Format: Master Thesis
• Language: English
• Published: Norwegian University of Life Sciences, Ås 2016
• Subjects: Norwegian glacier; Hellstugubreen; glacier foreland; plant establishment; seed germination; survival- and dispersal limitation; Norsk isbre; isbre-forland; smeltande isbrear; planteetablering; frøspiring; overleving- og spreiingsavgrensing; VDP::Mathematics and natural science: 400; Norway; Inga; Pioner; Beckwithia glacialis; glacier; Poa alpina
• Online Access: http://hdl.handle.net/11250/2403667

Glaciers are melting and retreating on a global scale due to climate change. Rapid glacier retreat leave behind large areas of barren ground, in which primary succession and plant establishments can start. However, a typical feature in glaciers forelands is that vascular plants are lacking in a distinct area close to the front of melting glaciers. To explain the absence of plants in this unpopulated area, I have conducted seed sowing, transplantation, and soil seed bank experiments to explore the establishment and survival success in eight pioneer species (i.e. Saxifraga stellaris, Poa alpina, Poa arctica, Oxyria digyna, Arabis alpina, Cerastium cerastoides, Arabis petraea and Beckwithia glacialis) along a chronosequence in the glacier foreland of Hellstugubreen in Jotunheimen, central Norway. Interestingly, my results from the field experiments showed that the study species generally had significantly higher germination success, survival, vitality and better performance in the unpopulated area nearest to the glacier as compared to in the positions furthest away from the glacier. Moreover, the soil seed bank experiment revealed that there was no seed bank in the unpopulated area closest to the glacier front. From these results, I draw the main conclusion that dispersal limitation, and not germination- and survival limitations, explained the absence of plants in the unpopulated area in front of the Hellstugubreen glacier. In addition, to understand what environmental factors that limits the growth of the important pioneer species, i.e. A. alpina, I conducted a growth experiment under four controlled combinations of temperature and light conditions. Here, my results showed that A. alpina grew better under cold and high light conditions, and that the proportion of fertile individuals were significantly reduced with increased temperatures. Isbrear smeltar og trekkjer seg tilbake globalt grunna klima endringar. Når isbrear trekkjer seg raskt tilbake blir det lagt att eit stort område av naken grunn der primærsuksesjon og plantekolonisering kan byrja. Men eit typisk karakteristikk på isbre-forland er mangelen på vaskulære planter i eit klart område framom isbrefronten på ein smeltande isbre. For å forklare manglelen på planter i detta område utan busetnad, gjorde eg eit såfrø-, transplanterings- og jord frøbank eksperiment for å utforske etablering og overlevingssuksess hjå åtte pioner artar (som Saxifraga stellaris, Poa alpina, Poa arctica, Oxyria digyna, Arabis alpina, Cerastium cerastoides, Arabis petraea and Beckwithia glacialis) langs ein tidsserie i isbreforlandet av Hellstugubreen i Jotunheimen, i sentral Noreg. Mine resultat frå felteksperimenta viste interessant at studieartane hadde generelt signifikant høgare spiringssuksess, overleving, vitalitet og betre yting i det området utan busetnad nærmast isbreen, samanlikna med i posisjonen lengst unna isbreen. I tillegg, viste jord frøbank eksperimentet at det var inga frøbank i det området utan busetnad nærmast isbreen. Frå dessa resultata, trakk eg hovudkonklusjonen at det var spreiingsavgrensing, og ikkje spirings- og overlevingsavgrensing, som forklara mangelen på planter i det området utan busetnad ved fronten av Hellstugubreen isbre. I tillegg, for å forstå kva miljøfaktorar som avgrensar vekst hjå den viktige pionerarten A. alpina, gjorde eg eit veksteksperiment under fire kontrollerte kombinasjonar av temperatur og ljos forhold. Her viste resultata at A. alpina veks betre under kaldt og høgt ljos forhold, og at andelen fertile individ vart signifikant redusera med høgare temperatur. M-ECOL