Interactions between a cushion plant (Azorella selago) and surface sediment transport on sub-Antarctic Marion Island

Abstract

a b s t r a c t a r t i c l e i n f oOn sub-Antarctic Marion Island cushions of the dominant vascular plant species, Azorella selago, interact with the geomorphology of fellfield landscapes by affecting sediment distribution and ultimately terrace formation. Here, to understand the consequences of Azorella cushions for substrate movement and sorting, we quantified the size and shape of Azorella cushions and the grain size distribution of sediment surrounding these cushions, using a combination of image analysis approaches. Results show that as cushions become larger, they tend to become more elongated and grow more perpendicular to the slope. Mean and variance of grain size were greater upslope of Azorella cushions, while the number of particles was higher downslope of cushions, although these differences were not significant at all sites studied. Differences between upslope and downslope particle sizes were, however, not related to cushion elongation or growth angle as had been expected. The observed sediment partitioning is likely caused by a combination of frost-related sediment transport and Azorella cushions acting as sediment obstructions. Understanding these interactions between Azorella cushions and the landscape is especially important in the light of recent warming and drying on the island, as particle size affects soil properties such as water-holding capacity and frost susceptibility.

The spatial structure of Antarctic biodiversity

“…These features are characterized by a gradient of stability from fine, unstable material to larger stones around the edge. The latter also tend to accumulate snow, providing both water and a substratum for microbial and vegetation community development (Engelen et al 2008, see also Haussmann et al 2009). …”

Biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern Cascades, California

“…6A, 3); in addition, these linear areas often experience accelerated downslope shift (Pérez, 1990c(Pérez, , 2009a. Similar sediment rerouting around plants has been reported for slopes in Spitsbergen (Smith, 1956), the equatorial Andes (Pérez, 1987b), France (Bertran and Texier, 1999;Arquès, 2005), and the sub-Antarctic (Haussmann et al, 2009).…”

7.31 Hillslope Processes in Cold Environments: An Illustration of High-Latitude Mountain and Hillslope Processes and Forms

“…Diurnal frost creep in the sub-Antarctic creates high rates of soil surface disturbance that limit seedling establishment and may lead to vegetation dieback (Boelhouwers et al, 2003). Vegetation itself leads to microclimatic changes that result in spatial heterogeneity in soil frost intensity and resulting creep rates (Haussmann et al, 2009b). Vegetation itself leads to microclimatic changes that result in spatial heterogeneity in soil frost intensity and resulting creep rates (Haussmann et al, 2009b).…”