Holocene upper tree-limits of Pinus section sylvestris in the Western Alps as evidenced from travertine archives

Abstract

The postglacial dynamics of Pinus sylvestris, Pinus mugo and Pinus uncinata are poorly documented in the Alps due to a lack of precise taxonomic resolution. We present past altitudinal distribution of these pine species, at a local scale, based on morphometric and taxonomic analyses of fossil cone imprints preserved in travertine deposits from the mountain and subalpine belt in the Western Alps. We found that P. sylvestris and P. uncinata have been present in the study area since at least 11,500 calibrated yr BP. Until 8500 cal yr BP, these conifers occupied likely a wide altitudinal range, favoured by the establishment of drier and warmer climate conditions compared to present-day. After this period, the dynamics and spatial distribution patterns of P. sylvestris and P. uncinata were strongly shaped by the expansion of more competitively superior conifers that had contributed to their local extinction from several sites and the fragmentation of their population.