Reconstructing terrestrial climates using quantitative palaeoecology. Case studies from the high-altitude alpine Holocene and the last glacial and interglacial extremes in N-Italy and Slovenia.

Microscopic remains (pollen, spores, algae, insect remains, etc.) stored and preserved in sedimentary sequences over geological time periods provide a wide spectra of "response variables" (Birks et al., 2010) of past terrestrial and aquatic habitats. But, while the suitability of paleoecological records for qualitative environmental reconstructions is widely accepted, their potential as quantitative climate predictors is still poorly explored. Within the CNR-DTA "Nextdata Project" we tested the feasibility of reconstructing past temperature and precipitation series using terrestrial fossil pollen records from lake and mires located in Northern Italy and nearby areas. Climate parameters are estimated through updated numerical procedures comparing fossil pollen spectra with modern datasets. We applied several modern calibration subsets, obtained from a recently issued version of the European Modern Pollen Database (EMPD, Davis et al., 2013) New altitudinal training sets, recording ecological and climate gradients in the Alpine region, are being sampled and integrated within the EMPD to obtain transfer function for paleoclimate reconstructions. Techniques of regression and calibration (Locally-Weighted Weighted-Averaging - LWWA, Weighted Averaging - WA; ter Braak & Barendregt, 1986; Juggins & Birks, 2012) and the assemblage approach (Modern Analogue Technique - MAT; Juggins & Birks, 2012) are applied to pollen assemblages and used to constrain model uncertainties and to validate the models. Pollen-inferred quantitative climate estimations of past climate variables (temperatures and precipitation) will be presented from: (i) a high-elevation site in the western Alps (Rutor Glacier foreland; Badino, 2016) bearing paleobotanical evidence of an Holocene climate optimum and the thermal decline at around 4000 yrs cal BP; (ii) the Last Interglacial at Lake Fimon (Pini et al., 2010) where the development of forest vegetation after the treeless-steppe phase of the penultimate glaciation is documented. Here, mixed deciduous woodlands of warm-temperate and dry climate are replaced by mixed Abies-Fagus-Carpinus betulus forests of oceanic-temperate signature chronologically constrained during a phase of insolation minima. This climatic pattern is captured in the pollen-based reconstructions so far obtained; (iii) pollen and macroremains from a continuous sediment record spanning most of the Last Glacial Maximum at the slovenian fringe of the Alps. Here, the pollen and charcoal record of open forests with boreal signature provides several predictors of cold-temperate continental ecosystems, extinct in the Alps but finding appropriate analogues along ecological gradients in Fennoscandia and Siberian ranges.