The ombrotrophic peat bogs of Tierra del Fuego are located within the southern westerly wind belt (SWWB), which dominates climate variability in this region. We have reconstructed late-Holocene water-table depths from three peat bogs and aimed to relate these records to shifts in regional climate. Water-table depths were quantified by the analysis of testate amoeba assemblages, and a regional transfer function was used to infer past water-table depths. During the last 2000 years, testate amoeba assemblages have been relatively stable, with a dominance of Difflugia pulex and Difflugia pristis type, and an increase in Assulina muscorum and other Euglyphida at the top of each section. Multivariate analyses show that water-table depth remained the main environmental variable explaining assemblages along the TiA12 core, but reconstructions were not significant for the two other cores. In line with the low variability in assemblages, water tables were relatively stable during the last 2000 years. Slightly wetter conditions were found between ~1400 and 900 cal. BP and a pronounced recent dry shift was reconstructed in all of the three peat profiles. Considering the regional climatic context, this recent shift may have been forced by a decrease in precipitation and warmer conditions linked to an increase in the importance of the SWWB. Nevertheless, we cannot exclude the influence of higher UV-B radiation resulting from the local degradation of the ozone layer since the late 1970s, which may have had an additional effect on the relative presence of A. muscorum in the southern Patagonian region.
We thank Ricardo Muza and the Wildlife Conservation Society (WCS) Karukinka Park rangers for facilitating access to Karukinka Park. We also thank François De Vleeschouwer, Gaël Le Roux, Heleen Vanneste, Sébastien Bertrand, Zakaria Ghazoui and Jean-Yves De Vleeschouwer for fieldwork assistance. Nelson Bahamonde (INIA, Punta Arenas, Chile) and Ernesto Teneb (UMag, Punta Arenas, Chile) provided logistical support for the fieldwork in Chile. Dr Andrea Coronato (CADIC, Ushuaia) kindly provided logistical support for the research in Argentina. We also thank Ramiro Lopez for fieldwork assistance, Claudio Roig for access and permission to sample Tierra Australis and Audrey Innes for laboratory assistance. We appreciate the critical reviews by Graeme Swindles and an anonymous reviewer which improved the manuscript.
Funding This work was supported by the Natural Environment Research Council (grant numbers NE/I022809/1, NE/I022981/1, NE/I022833/1 and NE/I023104/1).
- Assulina muscorum
- Southern Annular Mode
- southern westerly wind