Date of Award

Fall 10-19-2018

Level of Access

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Jacquelyn Gill

Second Committee Member

Jasmine Saros

Third Committee Member

Hamish Greig

Additional Committee Members

Brenda Hall

Michael Polito

Abstract

The Falkland Islands are a biodiversity hotspot in the South Atlantic Ocean, with some of the world’s most important populations of seabirds and seals. The impact of climate change on these marine populations and their coastal breeding habitat in the Falklands is unknown. Coastal grasslands of Poa flabellata (tussac grass) form critical breeding habitat for wildlife, but have been heavily degraded by the introduction of livestock in the 17th century. This dissertation investigates the impacts of global change (climate change, grazing) on P. flabellata and its sensitivity to the fecal nutrient subsidies provided by marine wildlife. Chapter 1 provides the first multi-proxy reconstruction of past environmental change to understand how marine animals breeding in the Falklands responded to climate change over the past 14,000 years. At ~5,000 years ago, seabird and/or seal populations reached higher levels than the previous 9,000 years at Surf Bay, East Falkland Island. Fires were present throughout the past 14,000 years, but fire activity was highest when marine-derived nutrient input into the coastal grasslands from seabirds and/or seals increased. The increase in marine-derived nutrients and fire coincided with an increase in grasses, as well as the onset of neoglaciation. This reconstruction suggests that the Falklands are a refuge for seabirds and/or seals during cold periods in the past, and that marine-derived nutrients are important for improving coastal grasslands. It remains unknown whether tussac grass or other grasses species responded to changes in marine-derived nutrient input in our paleoecological reconstruction. Thus, in Chapter 2, I found that phytoliths and not pollen of modern native grass species are useful in distinguishing tussac grass from other species, supporting future investigations of the response of tussac grasslands to global change. Chapter 3 examines the potential for P. flabellata, which forms extensive peat records, as a new paleoclimate proxy in the South Atlantic where other archives for paleoclimate reconstructions (i.e. tree ring records and ice cores) are absent. Through a year-long modern calibration study, I found that tussac grass tissues record inter-seasonal environmental changes in temperature and humidity, though not precipitation source. Thus, this study warrants the use of tussac grass peat records to fill in a significant gap in our knowledge of paleoclimate in the South Atlantic Ocean. Chapter 4 provides an assessment of the impact of modern and historic grazing on soils and plants in the ecologically important coastal tussac grasslands. After release from grazing, tussac grasslands recovered rapidly, and marine-derived nutrient subsidies may be critical to improve restoration efforts. Overall, this work suggests that the terrestrial-marine linkage in the Falkland Island is sensitive to both climate change and land use change.

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