Quantifying postglacial climate and vegetation dynamics of the forest-steppe ecotone in northern Patagonia, Argentina
funded by the German Research Foundation, DFG (personal grant FO 801/3-1), in collaboration with Thomas Giesecke, Univ. of Göttingen and Simon Brewer, Univ. of Utah; 2016-2019
Vegetation responds to both average climatic conditions and extremes, thus changes in past vegetation make a good indicator for past climate changes. Ecotonal regions are particularly sensitive to climate change, although fire and other feedback mechanisms may delay responses of the vegetation to climate change. This project looks at the vegetation composition along climate gradients in space as well as through time. We aim to arrive at a better understanding of the dynamics of the ecotone and past climate change studying the vegetation internal processes and responses to disturbance such as fire.
The study focuses on the forest-steppe ecotone in northern Patagonia, Argentina at around 39 degrees south. Modern pollen samples from small to medium sized lakes at different elevations are used a) in the construction of climate transfer functions, and b) to obtain pollen representation factors to better quantify past vegetation change. Climate variables for the transfer functions will be obtained by monitoring soil moisture and temperature around those lakes from which modern pollen samples are collected. This approach will provide information about the mean and the variation of these parameters, necessary as the study region contains strong climate gradients over short distances.
Pollen and charcoal will be analysed from sediment cores in three sites across the forest-steppe ecotone: 1 Lake Torta; 2 Lake Tonkol; 3 Mallin Piedra Pintada
Preliminary pollen data indicate several gradual changes as well as a strong shift in the ecotone around 6000 years ago. The extent of this shift and other changes is potentially masked due to the overrepresentation of Nothofagus pollen. The application of representation factors and models of pollen dispersal and deposition will help to quantify the extent and dynamics of this and other cases of postglacial vegetation change. The detailed reconstruction of the vegetation dynamics will be used to evaluate the quantitative climate reconstruction from the sites. In addition, this information will increase the understanding of ecotonal vegetation dynamics, supporting and contributing to conservation strategies for the National Parks of the region.
PhD students Ricardo Moreno and Jessica Moreno are contributing to this investigation. The project is a contribution to the PAGES working group LandCover6k