Human impact on vegetation at the Alpine tree-line ecotone during the last millennium: lessons from high temporal and palynological resolution

A multi-proxy, high-resolution record of peatland development and its drivers during the last millennium from the subalpine Swiss Alps

“…Kamenik et al (2009) found a strong link between mean AprileNovember temperatures and pollen assemblages in a sub-decadally resolved part of the sequence (AD 1864e2003), which we interpret as temperature forcing on the flowering capacities of the plant populations rather than fluctuations in population density. In a comparable pollen study, van der Knaap and van Leeuwen (2003) came to the same conclusions for the last century in the northern and central Swiss Alps. Records of multi-decadal temporal resolution like that of the early and middle period of Mauntschas mire (before ca.…”

“…Among them, peatlands in mountains are generally given little attention, even though they differ markedly from lowland peatlands (Succow and Joosten, 2001) and were shown to be sensitive to climate change and human impact on decadal to millennial time scales. During the last few centuries, most mires in the Alps were repeatedly impacted by human action (Sjögren et al, 2007), but some were shown to be controlled by climate during the twentieth century (van der Knaap and van Leeuwen, 2003).…”

“…One objective is to find climate signals, as the mire lies close to the forest-limit ecotone where climate may be limiting for a number of organisms and processes. We aim at high temporal (near-annual) resolution, as this brings phenomena to light that are otherwise missed (van der Knaap et al, 2000;van der Knaap and van Leeuwen, 2003).…”

“…Differences in spatial scale arise when including proxies transported by wind, such as pollen, spores, and charcoal. These proxies reflect environmental changes from within a few meters to many kilometers (Sugita, 1994;Sjögren et al, 2010; van der Knaap et al, in press). In contrast, most macrofossils remain where they were formed, as they represent the material the peat is built of (Sphagnum and other mosses, roots, stems).…”

“…For quantification, each sample was spiked with Lycopodium (Stockmarr, 1971). Identification of microfossils followed van der Knaap et al (2000). Charcoal particles >10 mm were counted together with the microfossils.…”