Temperature dynamics in mire ecosystems on Marion Island

Abstract

The sub-Antarctic tundra is sensitive to disturbance due to its composition and scarcity of species. The Mire Complex on Marion Island which constitutes half of the area below 300m.a.s. l is a very important habitat for temperature dependant graminoids, mire bryophytes and moss species. Preliminary temperature measurements at depth in five separate mesic mires at different locations on Marion Island indicate that mires on the western side of the island are warmer in both winter and summer and mire temperatures in the east are colder and more variable. Temperature records show that it is the top layer of the mire that are the most thermal variable and that a seasonal reversal in temperature gradient with depth exist. It is suggested that this reversal is due to the seasonal changes in solar radiation inputs into the mire and that the passages of synoptic scale weather systems influence the diurnal radiative and sensible heat exchanges in the top layers. This diurnal radiative and sensible heat fluxes are, therefore, superimposed on the seasonal changes in the energy budget. Climate change implications for sub-surface mire dynamics on Marion Island show that if a continuous warming trajectory remains and the current changes in synoptic scale weather patterns persist, a further warming trend in mire temperatures must be expected. This in turn will influence the respiration rates of mire soils and soil decomposition potentials, ultimately threatening the variation of biotic communities within mire ecosystems. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.