Small scale spatial and temporal variability of microclimate in a fellfield landscape, Marion Island

Sammanfattning: Marion Island is situated in the South Indian Ocean and belongs to the sub-Antarctic island group, Prince Edward Islands. The islands in the sub-Antarctic have over the past few decades been exposed to a warmer and drier climate trend. The aim of this thesis is to achieve better understanding of the small-scale spatial and temporal variability between Azorella selago andthe surrounding microclimate. Due to the consequences of climate change, the interactions between Azorella selago, landforms and soil processes are important for the future of the terrestrial ecosystems in the sub-Antarctic. The theory part in this thesis describes different processes and features that are essential to understand the context of this thesis. The energy balance and the insolation is shown to be an important aspect when looking at the spatialvariability of the microclimate. The summary of the results in the thesis is based on temperature and moisture measurements within two grids. One on the east and one on the west side of the island The most important result from the measurements is that different weather conditions create different situations for the microclimate. The weather condition ‘sunny no wind’ created a high spatial variability in temperature on the ground, which was completely absent during overcast days. Temperature variability is highly dependent on cloud cover according to these results. Moisture changes also seem to be less weather dependent than temperaturechanges. The data provide a first confirmation that an increase in sunshine hours gives increased spatial variability in temperature (not moisture) and soil frost. An increase in spatial variability of the microclimate within small areas could give rise to an expansion in the patchiness of soil frost processes in the landscape. The representivity of single point measurements of ground surface temperature should be questioned. Patterns of areas with low moisture content within the grid correlate with points where measurements were taken on Azorella selago. The Azorella cushion could, according to the results of this thesis, be associated with dry areas within the grid. Azorella selago is thereby suggested to increase the spatial variability of moisture and also contribute to a locally drier microclimate. Moisture variability varies more between the east and west side of the island, than that it is weather dependent. Shaded areas show a pattern of lower temperature than for the other variables under sunny conditions. If more shaded areas are created by for example landforms like Azorella selago or solifluction deposits, the temperatures would probably be lower and also create a wider spatial variability. This study provides first data on the important interactions between Azorella selago and how it affects through spatial variability in micro-climate, ground frost potential and resulting soil disturbance by frost creep and solifluction.