Sedimentary pollen, charcoal and plant macrofossil analyses with high resolution and precision suggest a strong shift in vegetation composition during the early to mid-Holocene transition in the upper mountain belt. At Piano mire (1439 m above sea level (a.s.l.), Ticino, Switzerland) forests were dominated by Abies alba during the early Holocene (prior to ca. 8000 cal. a BP). Abrupt collapses of A. alba at ca. 7800–7400 cal. a BP enabled the expansion of the light-demanding pioneer Betula. Afterwards A. alba populations regained their previous abundance in the forests. Within the dating uncertainties of our record we assume that a unique combination of wet and cold years between 8400 and 7500 cal. a BP led to repeated lethal disadvantages for Abies. Our record of Abies oscillations is in good biostratigraphic agreement with the record that has been used to define the Misox cold event (Pian di Signano, 1540 m a.s.l.), which has been previously correlated with the 8200 cal. a BP event. Given the age estimates of the Abies collapses in our well-dated record, our results suggest that additional efforts are needed to understand the linkage between the Misox and the 8200 cal. a BP event. They imply a high sensitivity of mountain vegetation far below the tree line (∼800 m) to Holocene climatic changes of about 2°C in annual air temperature. Copyright © 2010 John Wiley & Sons, Ltd.