Chrono-Environment

Interdisciplinary research was carried out in mid-level mountain areas in France with the aim of documenting historical mining and smelting activities by means of pollen and geochemical analyses. These investigations were made on cores collected in French peatlands in the Morvan (northern Massif Central), at Mont Lozère (southern Massif Central) and in the Basque Country (Pyrénées). Different periods of mining were recognised from Prehistory to modern times through the presence of anthropogenic lead in peat. Some of these were already known from archaeological dates or historical archives, especially for mediaeval and modern periods. However prehistoric ancient mining activities, as early as the Middle Bronze Age (ca. 1700 b.c.), were also discovered. They had all led to modifications in plant cover, probably related in part to forest clearance necessary to supply energy for mining and smelting.

This paper aims to reconstruct the vegetation history of a middle mountain -the Morvan (Burgundy, France) -since the Neolithic (i.e. 7000 years). The results of palynological and non-pollen palynomorphs (NPPs) analysis performed on 10 peat cores document the main phases of human agro-pastoral practices and natural resources management which drove the formation of the cultural landscape of the Morvan Massif over time. To document the history of human activities at a regional scale, particular attention was given to the determination, the characterization and the graphical depiction of phrases of human impact. Both the quantification of the impact of human pressure and the chronological uncertainty of the different phases identified by pollen and NPP analysis were taken into account. This study reveals a clear human presence during periods that were formerly poorly documented, such as the onset of the Neolithic period, the Bronze Age, the early Iron Age and the early Middle Ages. It also sheds new light over periods for which there is better archaeological and historical knowledge, such as the widespread occupation of the massif in the late Iron Age, the cultivation of chestnut from the 11th to the 16th century and the impact of modern firewood exploitation on the forest.

NEW PALAEOECOLOGICAL DATA PROVIDED BY THE PREMERY FOREST CLOSED DEPRESSIONS (BURGUNDYFRANCE)
The closed depressions (CDs) located in the Premery forest on the Nivernais Plateau (Burgundy, France) are suitable natural
archives for palaeoecological studies as formerly demonstrated in the sixties. New pollen and non-pollen palynomorphs (mainly
algal and fungal remains) analyses performed on two  sequences, give complementary information about the context of the CDs infilling formation, and the vegetation dynamics on the Nivernais Plateau. The two cores chronologically complete each other: the first one concerns the Late Glacial and the Early Holocene (from 16 000 to 10 000 cal. yr BP), but it is less suitable for Mid- and Late Holocene because of hiatuses in the sedimentation. The second one documents only the end of the Late-Glacial period (Younger Dryas), but it continuously covers the whole Holocene. Concerning human impact, the indicators of agro-pastoral activities are very scarce and punctual during Prehistory and Bronze Age (from ca 5 000 to 800 BC). Even after this date, and despite further deforestation phases occurring during the Iron Age (800-50 BC), the classical Middle Ages (around 1000 AD) and the Modern period, the woodland remains dominant, and proximal pollen and fungal indicators of human activity are only present in one core, from the 16th to the beginning of the 19th century. However, the forest might be affected for other reasons than agro-pastoral purpose, such as fire wood, timber wood, palaeo-industries… If these two CDs have comparable evolutions during Late-Glacial and Early Holocene, running from a state of small pond to small peat bog, their later histories are different. This fact shows the role of the catchment area variability for each CD infilling process, and it highlights the very local value of each of the palaeoecological information they provide.

High altitude lakes are vulnerable ecosystems that require protection and sustainability management, although their overall functioning is still poorly understood. In France protected area managers and scientists are cooperating to address this problem. Their results show the huge diversity of these altitude lakes and imply specificities in their functioning and in the way they respond to stressors. Multidisciplinary studies on these ecosystems, on their individual history and the stressors they face, need to be developed in a number of lakes, alongside long-term monitoring surveys. This is the objective of the Sentinel lakes network.

Understanding the processes that led to the recent evolution of Mediterranean landscapes is a challenging question that can be addressed with paleoecological data. Located in the White Mountains of Crete, Asi Gonia peat bog constitutes an exceptional 2000-years-long sedimentary archive of environmental change. In this study, we document the making of the White Mountains landscape and assess human impact on ecosystem trajectories. The paleoenvironmental reconstruction is based on high-resolution analyses of sediment, pollen, dung fungal spores and charcoal obtained from a 6-m core collected from the bog. Multiproxy analyses and a robust chronological control have shed light on anthropogenic and natural processes that have driven ecological changes, giving rise to the present-day Mediterranean ecosystem. Our results suggest that sediment accumulation began during the transition from the Hellenistic to the Roman period, likely due to watershed management. The evolution of the peat bog as well as vegetation dynamics in the surrounding area were linked to past climate changes but were driven by human activities, among which breeding was of great importance. Charcoal analysis reveals that fire was largely used for the construction and maintenance of sylvo-agropastoral areas. Pollen data allow the identification of three main vegetation assemblages: 1) evergreen oak forest (before ca. 850 AD), 2) heather maquis (ca. 850 to 1870 AD), 3) phrygana/steppe landscape. Rapid changes between phases in vegetation development are associated with tipping-points in ecosystem dynamics resulting from anthropogenic impact. The modern ecosystem did not get established until the 20 th century, and it is characterized by biodiversity loss along with a dramatic drying of the peat bog.

North Africa is the largest source of mineral dust on Earth, which has multiple impacts on the climate system; however, our understanding of decadal to centennial changes in African dust emissions over the last few millennia is limited. Here, we present a high-resolution multiproxy analysis of sediment core from high-elevation lake Bastani, in Corsica Island to reconstruct past African dust inputs to the Western Mediterranean area over the last 3150 yrs cal BP. Clay Mineralogy and geochemical data allows us to identify that terrigenous fluxes are almost exclusively related to atmospheric dust deposition from the West and North Sahara over this period, which is consistent with current observations. High resolution geochemical contents provide a reliable proxy of Saharan dust inputs with millennial to centennial scale variations. Millennial variations have been correlated to the long term southward migration of the Intertropical Convergence Zone (ITCZ) with an increase of dust input since 1070 yrs cal BP. This correlation suggests a strong link with ITCZ and could reflect the increased availability of dust sources to be mobilized with an increase in wind and a decrease in precipitation over West and North Africa. For centennial to decadal variations, wavelet analyses show that since 1070 yr cal BP, NAO is the main climatic forcing with an increase of Saharan dust input during positive phase, as suggested by previous study over the last decades. However, when ITCZ is in a northern position, before 1070 yr cal BP, wavelet analyses indicate that total solar irradiance (TSI) is the main forcing factor, with an increase of African dust input during low TSI. With climate reanalysis over the instrumental era, during low TSI we observe a significant negative anomaly in pressure over Africa which is known to increase the dust transport. These two climatic

Socio-ecological systems are complex, dynamic structures driven by cross-scale interactions between climate, disturbance and subsistence strategies. We synthetize paleoecological data to explore the emergence and evolution of anthropogenic landscapes in southwestern Europe and northern Africa. Specifically, we estimate trends in vegetation and fire, and assess how changes in climate and resource exploitation altered ecosystem dynamics over the last 10,000 years. Pollen data reveal that a complex vegetation mosaic resulted from the conversion of forests into areas suitable for crops, especially after 7000 cal yr BP. Cross-scale analysis shows a progressive decoupling of climate and ecosystem trajectories, which displayed an overall south-to-north time-transgressive pattern consistent with models of population expansion. As human impact increased, so did the use of fire, and after 4000 cal yr BP, levels of biomass burning became homogeneous across the region. This region-wide rise in ...

In the Mediterranean region, Corsica represents one of the most important hotspots of biodiversity, partly due to the high number of endemics species. This region is also one of the most affected by forest fires worldwide. The present vegetation is adapted to a wide range of disturbance regimes, but a change in fire frequency or intensity in the future may severely affect ecological resources and other socio-economical aspects. Here, we study the dynamics of vegetation–human–fire interactions for the past 12,000 years as recorded by Lake Bastani (Corsica, France). We used well-dated sedimentary records of charcoal, pollen and fungal spores to infer past fire regime, land cover and pastoral activities, respectively, and we compared our results with charcoal records from two other Corsican lakes (Nino and Creno, respectively). Our results suggest that climate and natural fires were the main factors shaping the landscape before 5000 cal. BP. Then, the extraordinary diversity of the cur...

Our understanding of climate and vegetation changes throughout the Holocene is hampered by biases in the proxy representativeness in sedimentary archives. Such potential biases are identified by comparing proxies to modern environments. Consequently, it becomes important to conduct multi-proxy studies and robust calibrations. The taiga-steppes of the Mongolian plateau, ranging from the extremely cold-dry Baikal basin to the Gobi desert, are characterized by low annual precipitation and continental annual air temperature as well as livestock grazing. The characterization of the climate system of this area is crucial for the understanding of Holocene Monsoon Oscillations. This study focuses on the calibration of proxy-climate relationships for pollen and glycerol dialkyl glycerol tetraethers (GDGTs) by comparing large published Eurasian calibrations with a set of 53 new surface samples (moss, soil and surface sediments). We show that: (1) preserved pollen assemblages are clearly imprinted on the extremities of the ecosystem range but mitigated and unclear on the ecotones; (2) for both proxies, inferred relationships depend on the geographical range covered by the calibration database as well as on the sample nature; (3) local calibrations, even those derived to the low range of climate parameters encompassed in the study area, better reconstruct climatic parameters than the global ones by reducing the limits for saturation impact, and (4) a bias in climatic reconstructions is induced by the over-parameterization of the models by addition of artificial correlation. We encourage the application of this surface calibration method to consolidate our understanding of the Holocene climate and environment variations.

This paper studies mire initiation modalities from the Late-Glacial to the Holocene by comparing radiocarbon ages on basal peat layers (112 sites from the Eastern French Massif Central e EFMC) with long-term land cover changes. We developed a semi-quantitative method based on the degree of openness and on Anthropogenic Impact Factors (AIF scores) from palaeoecological data (mire and lake records). Archaeological information was also considered to evaluate human impact. We compared regional mire development trends with datasets from Northern Europe, Siberia, Alaska and Canada, and with global CH 4 emission. Heterogenous cases of mire initiation were highlighted during the last 15 ka years in the EMFC. From 15 to 11.7 ka cal. BP, some mires and histic horizons occurred, although further research is needed to better understand these peat accumulation phases. Related to the Early Holocene warming, a mire generation established by terrestrialization, in the southern EFMC where geomorphology favoured fens. Bogs also formed by paludification in the whole area between 10 and 7 ka cal. BP. Then, various cases of mire initiation were found from 4.4 to 2.4 ka cal. BP. The high number of mires established since 2.4 ka cal. BP could be related to major anthropogenic changes, indirectly favouring fens (in former ponds for instance) or small bogs (at the back of roads, walls or in abandoned drainage systems). This last generation was typical of Western European mountains and implied that moderate human impact may also produce socio-ecosystems with high ecological value.

This paper presents an original palaeoparasitological study performed on samples from a sedimentary core in a peat bog (Asi Gonia, White Mountains, Crete, Greece). The aim of the study is to test the preservation and concentration of parasitic remains in peat sediments, to discuss animal presence around the site throughout the record, and to compare the results with other biomarkers of environmental history. In this aim, 22 sediment samples distributed between the Roman period and the present were processed and the residues were observed under light microscopy in search of parasitic markers (microscopic eggs or oocysts). The majority of the samples (86.4%) tested positive for the presence of helminth eggs. Several taxa were observed throughout the studied period, including Trichuris sp., Ascaris sp., Capillaria sp., Fasciola sp., Paramphistomum sp. and Macracanthorhynchus sp. The assemblage of parasite markers changes throughout the record and the variations show close correlations ...

Currently, indexes from the Fire Weather Index System (FWI) are used to predict the daily fire hazard, but there is no reliable index available in the Mediterranean region to be compared with paleofire records and check for their long-term reliability. In order to assess the past fire hazard and the fire-season length, based on data availability and requirements for fire index computation, we first chose and tested the efficiency of the Drought Code (DC) in Corsica (the main French Mediterranean fire-prone region) over the current period (1979–2016). We then used DC as a benchmark to assess the efficiency of the Monthly Drought Code (MDC) and used it to assess the Fire-Season Length (FSL), which were both used to characterize the fire hazard. Finally, we computed the Holocene MDC and FSL based on the HadCM3B-M1 climate model (three dimensional, fully dynamic, coupled atmosphere-ocean global climate model without flux adjustment) datasets and compared both index trends with those fro...