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"These palaeolimnological records, which span thousands of years, suggest that these current taxon-specific shifts are in response to an overriding effect of climate and, perhaps, they are an early indication of expected abrupt and general ecosystem shifts (Barnosky et al. 2012). In fact, Holocene and Late Glacial sediment records show that abrupt and large vegetation changes may occur in response to climate fluctuations within the range projected for the coming decades (Giesecke et al. 2011 "
[Show abstract][Hide abstract] ABSTRACT: Over recent decades, palaeolimnological records from remote sites have provided convincing evidence for the onset and development of several facets of global environmental change. Remote lakes, defined here as those occurring in high latitude or high altitude regions, have the advantage of not being overprinted by local anthropogenic processes. As such, many of these sites record broad-scale environmental changes, frequently driven by regime shifts in the Earth system. Here, we review a selection of studies from North America and Europe and discuss their broader implications. The history of investigation has evolved synchronously with the scope and awareness of environmental problems. An initial focus on acid deposition switched to metal and other types of pollutants, then climate change and eventually to atmospheric deposition-fertilising effects. However, none of these topics is independent of the other, and all of them affect ecosystem function and biodiversity in profound ways. Currently, remote lake palaeolimnology is developing unique datasets for each region investigated that benchmark current trends with respect to past, purely natural variability in lake systems. Fostering conceptual and methodological bridges with other environmental disciplines will upturn contribution of remote lake palaeolimnology in solving existing and emerging questions in global change science and planetary stewardship.
Journal of Paleolimnology 03/2013; 49(3-3):513-535. DOI:10.1007/s10933-013-9681-2 · 2.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Precise and accurate reconstructions of past environmental parameters from high-quality palaeoenvi-ronmental studies are critical for realistic testing of climate models. To ascertain the reliability of the reconstructions of the past, cross-validation from a variety of proxies and methods is essential. Mid-Scandinavia, showing a variety of palaeoecological studies, is a suitable region for comparing and validating environmental reconstructions. Here, pollen-based transfer-function reconstructions show inconsistent late-glacial temperature patterns. They also show that the Holocene Thermal Maximum (HTM) occurs at ca. 7.5–4.5 cal. ka B.P. However, thermal indicators (pollen, megafossils, plant macrofossils) place the HTM at no later than ca. 10–7.5 cal. ka B.P. It is argued that after the onset of the early Holocene warming equilibrium between vegetation and climate was established over a prolonged period; i.e. ca. 1,500 and 4,000 years in the mountains and lowlands, respectively. In the mountains, soil drought, wind and winter stress were important factors causing the lag, whereas inter-specific competition and soil development delayed the succession within the species-diverse lowland forests. These lags when vegetation was not filling its thermal potential result in a distortion of the temperature signal as derived by transfer functions which assume that vegetation is essen-tially in equilibrium with climate. Due to widespread human impact and erosion today, many modern training set samples are unsuitable as reference material for past environmental conditions. Various recommendations are suggested towards making improvements in the pollen-transfer func-tion approach to climate reconstructions. To overcome the difficulties resulting from vegetation lags in the early Holocene, proxies that have a faster response time to cli-mate, such as chironomids and aquatic plants including algae, may replace terrestrial pollen.
Vegetation History and Archaeobotany 05/2012; 22(3). DOI:10.1007/s00334-012-0360-4 · 2.65 Impact Factor