Peter le Roux


B.Sc. (Ecology) – University of Pretoria (1998-2000)
B.Sc. (Hons) (Zoology) – University of Pretoria (2001)

Research interests

My research interests are still expanding and are far from fixed because of the relatively short time I have been involved in ecology. Aspects which have been particularly interesting and exciting to me include community ecology, macro-ecology, the interaction between local and regional processes, and the interactions between ecosystem stability, diversity and functioning. This list is hardly complete and most of the branches of ecology in which I have had some experience interest me.

The view from just north of the base on Marion Island.

Two Azorella selago flowers. These flowers are only a millimeter ot two in diameter.

One of our higher altitude study sites (Tafelberg, on the eastern side of the island).

An Azorella Selago cushion from a high altitude site (Notice how densely other plants grow around it)

An Azorella Selago cushion from a low altitude site (Notice how only it is only cushions that have colonized this site).

An Azorella selago cushions from a mid altitude site (Notice how it’s right-handside has been colonized by the indigenous grass Agrostis magellanica).

Current Project

My M.Sc. project focuses on a fascinating species of plant – Azorella selago – and the effects of climate change on it. A. selago (known as a cushion plant, due to its compact, circular cushion-like appearance), is distributed across most of the sub-Antarctic region. This species is dominant in the fellfield vegetation type, which covers about half of the ice-free land surface in the sub-Antarctic. Fellfield, otherwise known as wind desert, is a harsh environment. My study site (Marion Island; see next paragraph) regularly experiences winds exceeding 100km/h, and has a mean annual temperature of about 6ºC. Fellfield soil is mostly composed of volcanic ash and weathered lava particles. Despite high rainfall (1500mm – 2500mm p.a.) the soil can be relatively dry, due to its high porosity. Additionally, most days the temperature in fellfield crosses the 0°C threshold – resulting in freeze-thaw events. With each freeze-thaw event, frost-heave (caused by the formation of needle-like ice crystals) can lift the upper soil surface, pushing rocks, plants and experimental equipment out of the soil! Despite these harsh conditions A. selago appears most healthy in this extreme environment. In mid-altitude fellfield, cushions provide a favourable habitat to other organisms, probably by buffering them against extreme temperatures and aridity. Other vascular plants often grow on A. selago cushions and the density of invertebrates is much higher in a cushion than on the surrounding ground.

The first component of my project involves documenting the variability shown by A. selago (focusing on its morphology, physiology, spatial structure and epiphyte load). Last year (2001) more than 900 cushions were measured and nearly 19’000 leaf samples taken from cushions growing on Marion Island (a little South African island, located nearly half way between Cape Town and Antarctica). It’s now my job to document how the morphology (using a number of variables including plant size and leaf area), physiology (variables include leaf nutrient content, growth rate), distribution (how the cushions are arranged relative to each other) and epiphyte load (the number and cover of plants growing on cushions) of A. selago varies across Marion Island. This baseline data is important for the next component of my project…

Climate change is predicted to be most extreme and most rapid at high latitudes. Indeed, over the last 30 years average temperatures have risen by 1.2°C and rainfall decreased by 20% on Marion Island (Smith 2002). The second component of my project is to test what effects changes in climate could have on A. selago. During April 2002, I applied a number of treatments to simulate potential changes in climate. With a lot of help from fellow researchers, clear polycarbonate sheets were erected over a number of cushions – these will reduce the rainfall received by some cushions, but not the temperature, humidity or light intensity experienced by the plants. Additionally, we expect that the higher temperatures being experienced on the island could lead to increases in epiphyte growth. For this reason, further cushions were covered with green shade-cloth to simulate what effect increased epiphyte growth could have on the cushions. In April 2003, I will be measuring various variables (representative of the morphology, physiology and epiphyte load of each cushion) on each of the treatment cushions to allow us to determine what effect changes in rainfall and light regimes are likely to have on A. selago.

Fellow researchers are looking at other aspects of the system. We hope that by the end of this project we will have a much more complete understanding of the fellfield ecosystems, as well as the ability to predict what effects climate change is likely to have on fellfield communities.

One of the polycarbonate sheets erected over a selected cushion. This construction will reduce the rainfall received by the cushion underneath it, simulating a reduction in rainfall.