Quantitative pollen- vegetation modelling of Patagonian High Andean steppe and Tree-line communities

TONELLO, M. S; PALACIOS, P.; BUNTING, M.J. ; MARCOS, M. A.; SOTTILE, G.D.; MANCINI, M. V.

Dublín

Congreso; 20th INQUA Congress; 2019

Understanding the long-term dynamics of high Andean steppe and upper tree-line communities in Patagonia is a key step in designing effective conservation and management strategies for these ecosystems in the face of expected climate changes. Pollen records covering the last 1200 years, which spans several ecologically significant climate changes in the region, are available, but applying landcover reconstruction methods to pollen records from Patagonia is still a challenge because these models are not yet parameterized for these habitats. Past work has shown that there are stable pollen-vegetation cover relationships for the main plants of interest (e.g. Burry et al., 2001; Sottile et al., 2016). This paper reports on the calibration of pollen dispersal and deposition models for the main plant types in this region, and their implications for the reconstruction of patch-scale dynamics at the upper tree line over the last 1200 years in response to known climatic drivers. A dataset of paired modern pollen surface samples and field and remote sensing vegetation data collected at multiple distance increments using a design which incorporates the wind regime of southern South America are analysed. Multivariate analysis of the pollen assemblages from the moss polster samples showed that the pollen types Nothofagus, Poaceae, Asteraceae subf. Asteroideae, Empetrum, Gaultheria, Apiaceae, Azorella, Mulinum and Nassauvia were the most important variables for separating forest and non-forest communities, and therefore for reconstructing past forest patch dynamics. Extended R-Value analysis is then used to estimate the Relative Pollen Productivity of these pollen types, using fall speed estimates based on measurement of at least 30 locally collected grains of each pollen type. Relevant Source Areas of Pollen are then explored for both moss polsters and for potential pollen record sources using both empirical and simulation approaches in order to estimate the spatial resolution possible for land cover reconstruction at this critical ecotone.Once the appropriate dispersal model is identified and calibrated, it can be applied both in simulation to explore the sensitivity of the pollen record to patch dynamics in this landscape and directly to the reconstruction of past land cover in this sensitive and biogeographically valuable region.