Year

2017

Degree Name

Doctor of Philosophy

Department

School of Biological Sciences

Abstract

Continental Antarctic vegetation communities represent good baseline environments for climate change research, with little human impact, simple trophic structures and fewer interactions than more complex ecosystems. They are expected to be more sensitive to environmental changes than communities in less severe conditions, however, continental Antarctic ecosystem responses to climate change are still uncertain, due to a paucity of available biodiversity data across the continent.

In the East Antarctic, changes to the Southern Hemisphere Annular Mode (SAM), primarily driven by the Antarctic ozone hole, have caused stronger circumpolar westerly winds, which have migrated poleward by 1-2° of latitude since the late 1970s. These winds have been linked to decreases in East Antarctic moss growth rates. Existing moribund and lichen-encrusted vegetation patterns in the Windmill Islands, East Antarctica suggest that this region is currently undergoing a period of long-term drying, with contraction of bryophyte communities to areas with reliable moisture supply. In order to assess recent vegetation changes in the Windmill Islands region, a long-term monitoring system was established in 2003.

Here, I present the results from the first decade (2003-2013) of repeat long-term vegetation monitoring at two sites in the Windmill Islands, East Antarctica (Antarctic Specially Protected Area 135 and Robinson Ridge), with the addition of data from a pilot study in 2000. Vegetation cover, health and species composition were assessed along a series of transects spanning a community gradient from pure bryophyte stands in the wettest areas, to drier lichen-dominated communities higher up the slopes.

Moss health state changes were observed and assessed as healthy, stressed and moribund over the decade of monitoring. A marked increase in stress and decline in health was observed in 2008, due to some stress event prior to the 2008 sampling. Moss health then further improved by 2013, with a return to baseline levels of health at ASPA 135, and regaining health to 2/3 of baseline levels at Robinson Ridge. Associated increases in the cosmopolitan species Ceratodon purpureus and moribund moss were found at both sites. This indicates that these vegetation communities are resilient, however moss can become moribund if stress is of high intensity or occurs for prolonged periods. The increase in the cosmopolitan moss species may lead to decreased abundance of the Antarctic endemic Schistidium antarctici, potentially causing concerns for conservation and management of these communities.

The methods and recommendations for future sampling protocols developed in this thesis will provide guidelines for future Antarctic vegetation monitoring programs, particularly for the Antarctic Near-shore and Terrestrial Observing System (ANTOS) monitoring network currently being developed. These methodologies are fast and effective, and can be implemented at the tiered levels of the ANTOS. If implemented across the continent, this would provide valuable data on vegetation biodiversity and change across the region. The current East Antarctic long-term monitoring system informs Australian State of the Environment Indicator 72, regarding terrestrial Antarctic vegetation. These results will help to inform policy and management of vegetation in the Australian Antarctic Territory.

FoR codes (2008)

0602 ECOLOGY, 0607 PLANT BIOLOGY, 0502 ENVIRONMENTAL SCIENCE AND MANAGEMENT, 0501 ECOLOGICAL APPLICATIONS

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.