Influence of vegetation on the ground thermal regime in continental Antarctica

Antarctica provides natural models that are influenced exclusively by climate change and/or other natural processes because the anthropogenic effects are negligible. The key environmental components of these ecosystems consist of vegetation and the underlying permafrost. The surface energy balance and, consequently, the ground surface temperature (GST) and ground thermal regime (GTR) can be influenced by vegetation, as is well known in Arctic areas. The interactions between vegetation, GST, GTR and their potential ecological implications in Antarctica have only recently begun to develop. This paper aims to contribute towards closing the gap of knowledge of these interactions. It does so by considering different spatial (intra-site and inter-site variability) and temporal (seasonal versus annual) scales with reference to dry and wet Antarctic cryptogamic tundra. For this reason, two sites and seven plots (bare ground versus vegetated ground) were instrumented and monitored in Victoria Land (continental Antarctica) to measure the ground temperature at different depths during the summer, as well as during one complete year. Our results demonstrate for the first time for continental Antarctica that vegetation provides an insulating effect with a net cooling effect on the GST varying with the vegetation type, structure, coverage and thickness. Independently of the GST, the soil thermal characteristics constitute the driving factor in determining the thickness of the active layer. We discuss potential future implications of changes in the vegetation, ground thermal regime and permafrost in a climate change scenario, with reference to the activation of feedbacks through changes in the energy balance, in the permafrost conditions and controls over ecosystem C storage and fluxes. (C) 2009 Elsevier B.V. All rights reserved.