| Summary: | Thesis (MSc)--Stellenbosch University, 2016. ENGLISH ABSTRACT: A database was compiled of structural and physiological traits for 25 vascular species and 17 bryophyte species on Marion Island (sub-Antarctic). The structural traits included leaf, stem and root characteristics and the physiological traits are all associated with photosynthetic responses to light and were measured using chlorophyll fluorescence quenching analysis. The data were subjected to principal component analysis and clustering analysis to construct a suite of plant functional types (PFTs). The correspondences between the PFTs and plant habit/taxonomy (forb, graminoid, fern, moss and liverwort), status (native to the island or introduced alien) and habitat (oligotrophic, manured or saline) were investigated using correspondence analysis. There were significant differences in most of the structural traits, but in only one of the photosynthetic traits, between sites at the same altitude and between altitudes. The between-site differences could not be explained since site characteristics were not measured, but the between site differences were often species-dependent; a particular species might show its lowest value for a particular trait at the same site where another species showed the highest value for that trait. The between-altitude differences in structural trait values could be ascribed to the effect of greater wind speed at higher altitude (lower stature, tougher leaves and stems). High altitude plants have greater specific root length, probably a response to low soil nutrient status and hence a need for foraging roots. However, plants in saline coastal habitats also show a high specific root length, probably in response to the inhibitory effect of high salt concentration on nutrient and water uptake. All the species except Azorella selago, the archetypical vascular species of high altitude were more stunted and showed greater signs of stress at high altitude than at low altitude. Native species tend to show greater values for those ...
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