Late Glacial and Holocene multi-proxy paleoecology in the Southern Carpathian Mountains: quantitative reconstructions and promising new molecular research directions

Abstract

<p>Over the last 10 years several alpine lakes were studied from the Southern Carpathian Mountains (SCM) using paleoecological, geochemical and stable isotope techniques. The aim of these studies were to obtain quantitative climate reconstructions for the alpine region for the Late Glacial (LG) and Holocene, reconstruct tree and timberline changes and examine how rapid climate change events manifested in this region, what are the regions characteristics. Absolute chronologies were also supported here for the first time with tephra chronology in the Early Holocene. In addition, environmental DNA studies were used to explore what molecular techniques can add to a more exact and often species level reconstruction of past floristic compositions. This talk will summarize these researches and use multivariate statistics to examine leads and lags in ecosystem response at multiple sites (Retezat, Pareng, Fogaras, Ciomadul Mts). These analyses first of all demonstrate that the amplitude of warming was attenuated in the SCM at the GS-2/GI-1 transition relative to NW Europe (~2,8-3 <sup>o</sup>C), summer temperatures increased abruptly already at 16.2 ka cal BP in direct response to the weakening polar circulation and the tripartite GS-1 had weak summer temperature decrease (<1 <sup>o</sup>C), but winter cooling was strong. Regarding the order of ecosystem changes, lead and lag analysis revealed <50 yr lag in vegetation response, 0-100 lag in aquatic floristic response and ~100-150 yr lag in aquatic faunal response to external forcing. Environmental DNA studies showed that despite the method is capable to better capture grass (Poaceae) floristic diversity and replicates woody specie composition obtained by plant macrofossil data, it fails to provide higher resolution for the herbaceous flora around the studied lakes that feature was explained partly by the incompleteness of reference DNA sequences for the trnL region and the DNA preservation characteristics of alpine lakes. Using these pioneer studies, several promising research directions were identified for this region: modelling of projected tree and timberline changes in combination with reconstructed data, using eDNA techniques to decipher alpine farming histories in the mountains and its impact on late Holocene tree and timberline change, reconstruction the accelerating speed of ecosystem change over the last 100 yr. in alpine lakes and calling attention for the irreversibility of these changes, demonstrating tipping points. These will be discussed in the presentation.</p>