Monitoring impacts of a changing climate on plant communities of Continental Antarctica

Background/Question/Methods

The high latitudes and altitudes are predicted to be affected first and most severely by climate change. The responses of ecosystems in these regions are thus expected to be an ‘early warning system’ for the impacts of changing climatic conditions. Antarctic communities have a relatively simple trophic structure and fewer interactions than elsewhere in the world, making this a particularly good baseline environment for climate change research. Major changes in Antarctic temperatures, wind speed and stratospheric ozone have already been observed and vegetation changes have already been documented in the maritime Antarctic, where temperature changes have been particularly pronounced. Vegetation changes throughout the majority of the continent, however, have yet to be reported, and improved monitoring and analysis of long-term data sets was recommended by the International Panel on Climate Change in 2007. Long term vegetation studies are made more difficult in Antarctica, due to the climatic extremes, however they are vital in establishing trends in plant growth, particularly due to the slow growth rates of Antarctic flora. Long-term monitoring of vegetation communities along a moisture gradient at two sites in the Windmill Islands, East Antarctica has commenced, in an area that supports some of the best-developed and most extensive plant communities on the continent. Vegetation in this region is solely based on cryptogams, mainly mosses and lichens. The endemic moss Schistidium antarctici dominates wetter habitats and extends into dry zones at low levels of abundance. The remaining bryophytes are cosmopolitan species, Bryum pseudotriquetrum occurring across the moisture gradient and Ceratodon purpureus restricted to drier habitats. 

Results/Conclusions

Vegetation species abundance analysis shows that the community composition has changed between 1999, 2003, 2008 and 2012. The observed changes are consistent with drying of the terrestrial communities leading to a decline in moss species that require available free water throughout the growing season, towards species that are more tolerant of drier areas, including both more desiccation tolerant mosses and lichen associations. Declining water availability appears to be the main driving factor of the observed changes in vegetation. Climate factors that could be responsible for reduced water availability include a significant decrease in the number of days where temperatures exceed zero during the summer growing season and increasing wind speeds. Our results indicate that this methodology is sensitive enough to detect climate-induced change in these slow growing communities.