Search

In order to better understand the long-term management of water resource and its relationship with peatlands in mid-mountain areas, a research project was conducted in the mire complex of Gourgon, in the Forez Mountains (Eastern Massif Central, France). The peat growth response to global and local changes was reconstructed based (1) on the radiocarbon dating of basal peat layers, (2) on the study of macrofossils and (3) on palynological analyses of key peat cores. This palaeoecological approach provided new answers to understand the development of the uplands and to fill the gaps between archaeological sites. Three major steps were identified during the last 3,000 years: (i) cultivation and pastoral activities from the Iron Age to the Roman Times; (ii) afforestation and predominant grazing during Late Antiquity and the Early Middle Ages; and (iii) major forest clearing motivated by cultivation needs (winter crops including rye – Secale cereale) during the Middle Ages. Comparison of lithological and palaeoecological data with topographical data and regional archaeological information highlighted that the anthropogenic diversion of streams, created to supply high-altitude farms, reduced the water flow in the valley and favoured the accumulation of peat for centuries. Thus, human activities were involved in the development of mire-valley ecosystems. This response of peatland ecosystems to human activities fits with a wider pattern of anthropogenically-induced peatlands in Central France. It underlines the importance of multidisciplinary and retrospective scientific studies in understanding the mechanisms of wetland evolution in the long-term.

Glacigenic perialpine lakes can constitute continuous post-last glacial maximum (LGM) geological archives which allow reconstruction of both lake-specific sedimentological processes and the paleoenvironmental setting of lakes. Lake Mondsee is one among several perialpine lakes in the Salzkammergut, Upper Austria, and has been previously studied in terms of paleoclimate, paleolimnology and (paleo)ecology. However, the full extent and environment of Late Glacial to Holocene sediment deposition had remained unknown, and it was not clear whether previously studied core sections were fully representative of 3D sediment accumulation patterns. In this study, the sedimentary infill of Lake Mondsee was examined via high-resolution seismic reflection survey over a 57-km extent (3.5 kHz pinger source) and a sediment core extracted from the deepest part of the lake, with a continuous length of 13.76 m. In the northern basin, seismic penetration is strongly limited in most areas because of abundant shallow gas (causing acoustic blanking). In the deeper areas, the acoustic signal reaches depths of up to 80 ms TWT (two-way travel time), representing a postglacial sedimentary sequence of at least 60-m thickness. Holocene deposits constitute only the uppermost 11.5 m of the sedimentary succession. Postglacial seismic stratigraphy of Lake Mondsee closely resembles those of well-studied French and Swiss perialpine lakes, with our data showing that most of Lake Mondsee’s sedimentary basin infill was deposited within a short time period (between 19,000 BP and 14,500 BP) after the Traun Glacier retreated from the Mondsee area, indicating an average sedimentation rate of about 1.4 cm/yr. Compared to other perialpine lakes, the seismic data from Lake Mondsee reveal little indication of mass movement activities during the Holocene. One exception, however, is rockfalls that originate from a steep cliff, the Kienbergwand, situated on the southern shore of Lake Mondsee, where, in the adjacent part of the lake, seismic profiles show mass transport deposits (MTDs), which extend approximately 450 m from the shore and are mappable over an area of about 45,300 m2. Sediment cores targeting the MTDs show two separate rockfall events. The older event consists of clast-supported angular dolomitic gravels and sands, showing high amounts of fine fraction. The younger event exhibits dolomitic clasts of up to 1.5 cm in diameter, which is mixed within a lacustrine muddy matrix. Radiocarbon dating and correlations with varve-dated sediment cores hint at respective ages of AD 1484 ± 7 for Event 1 and AD 1639 ± 5 for Event 2. As our data show no evidence of larger-scale mass movements affecting Lake Mondsee and its surroundings, we infer that the current-day morphology of the Kienbergwand is the result of infrequent medium-scale rockfalls.

The beginnings of the continuous human presence and of pastoral activities in the high mountainous region of Central Europe have recently become a frequently discussed topic in both archaeology and palaeoecology. In extreme environments such as the high Alpine main ridge and adjacent areas, highly adaptive subsistence strategies were required to exploit natural resources available in the subalpine and alpine zones. Such strategies were determined by changing environmental, social, and economic conditions. To investigate the relationships between settlement dynamics, human impact, and Holocene climatic changes, we studied the valleys of the Silvretta Massif in the central Eastern Alps between the Paznaun (Austria) and Lower Engadine valleys (Switzerland). We are presenting new archaeological, palaeoecological, and pedological evidence of continuous human activities from the Early Neolithic Period to the Bronze Age (~ 5,500–800 BC). This evidence sheds new light on the beginnings of intensified human impact on the high mountainous landscape, i.e. activities beyond Mesolithic hunting along the timberline. Archaeological data suggest a shift in subsistence strategies from hunting to herding at the end of the Neolithic Period (~ 2,800–2,500 BC). While palaeoecological data confirm this trend, they also indicate potentially earlier human and livestock impact through forest clearances by fire and grazing from about 4,200 BC onwards. In addition to archaeological sites and peat bogs, soils in high-altitude regions prove to be appropriate archives indicating former vegetation cover, shifts of timberline altitudes as well as disturbance of soil formation by human activity such as by slash-and-burn and by livestock grazing.

Twenty-two central European stonewort species and two species groups belonging to the genera Chara, Lychnothamnus, Nitella, Nitellopsis and Tolypella may be identified by oospores using a dichotomous determination key based on binocular and light microscope features. Size, shape, colour, membrane decoration and ridge number are used as identification criteria. A detailed oospore description for each central European charophyte species allows a reliable identification to the species or species group level. Because of the importance and wide distribution of stoneworts in aquatic plant communities, the identification of oospores may give information on ecological parameters such as water temperature, chemistry and light regimes in charophyte stands. Ecological changes due to climatic or anthropogenic impacts may therefore be elucidated for past and present freshwater ecosystems.