Article

2000-Year environmental history of a karstic lake in the Mediterranean Pre-Pyrenees: The Estanya lakes (Spain)

February 2004
CATENA 55(3):293-324

February 2004
55(3):293-324

DOI:10.1016/S0341-8162(03)00107-3

Authors:

Santiago Riera

University of Barcelona

Ramon Julià Brugués

Spanish National Research Council

The sediment record of the Estanya lakes (Pre-Pyrenees, Spain) indicates that this region was intensely affected by land use during the Middle and Modern ages, which contrasts with the present-day poor socioeconomic development of the region. The correlation between sediment and biotic data and well-known historical events suggests a reliable history of environmental changes in this area during the last 2000 years. Changes in lake level were mainly controlled by climatic factors, whereas properties such as lithology, organic carbon, ostracods and pollen content are mainly associated with lake management and land use. Major sedimentological changes resulted from the use of the lake for hemp retting at the start of the XIVth century. Subsequent depopulation of the area in the XXth century led to the progressive recovery of the lacustrine ecosystem.

Historical biogeography of Cannabis in the Iberian Peninsula: A probabilistic approach using palynological evidence

Article

Full-text available

Nov 2022
PERSPECT PLANT ECOL

The tempo and mode of colonization of the Iberian Peninsula (IP) by Cannabis sativa, its further internal spreading and the potential cultural and environmental factors involved remain unknown. The available continental-wide European meta-analyses using pollen and archaeological evidence account for only a few IP sites, insufficient for a sound assessment. This paper presents a nearly comprehensive database of almost 60 IP sites with palynological evidence of Cannabis and analyzes the corresponding spatiotemporal patterns. The first scattered records of this pollen type date from the Middle and Upper Paleolithic (150 to 12 ky BP) and would have entered the IP by maritime Mediterranean or terrestrial continental pathways, or both. A first burst of introductions, probably in a cultivated form, would have occurred during the Neolithic (7-5 ky BP) using similar paths. Human participation in these Neolithic introductions remains unclear but cannot be dismissed. A period of reduced Cannabis arrivals (mostly via Mediterraean pathway) occurred between the Chalcolithic and the Roman Epoch (4.5-2 ky BP), when the innermost parts of the IP were colonized (Late Bronze). A second, likely anthropogenic, introduction acceleration took place in the Middle Ages (1.5 ky BP onward) using the Mediterranean and the continental pathways. Maximum cultivation and hemp retting activity was recorded during the Modern Ages (16th-19th centuries), coinciding with the increased demand of hemp fiber to supply the Spanish royal navy for imperial expansion and commerce. A potential link between Cannabis colonization/introduction bursts and climatic warmings has been observed that should be tested with future studies. Regional moisture variations seem to be less influential. Further efforts to enhance and improve the database used in this study are encouraged. The results of this paper should be compared with archaeological and historical evidence to clarify the role of human migrations and cultural changes in the historical biogeography of Cannabis in the IP.

Historical biogeography of Cannabis in the Iberian Peninsula: palynological evidence

Preprint

Sep 2022

The tempo and mode of colonization of the Iberian Peninsula (IP) by Cannabis sativa , its further internal spreading and the potential cultural and environmental factors involved remain unknown. The available continental-wide European meta-analyses using pollen and archaeological evidence account for only a few IP sites, insufficient for a sound assessment. This paper presents a nearly comprehensive database of almost 60 IP sites with palynological evidence of Cannabis and analyzes the corresponding spatiotemporal patterns. The first scattered records of this pollen type, likely corresponding to wild Cannabis , date from the Middle and Upper Paleolithic (150 to 12 ky BP) and would have entered the IP by maritime Mediterranean or terrestrial continental pathways, or both. A first burst of introductions, probably in a cultivated form, would have occurred during the Neolithic (7-5 ky BP) using similar paths. Human participation in this Neolithic acceleration remains unclear but cannot be dismissed. A period of reduced Cannabis arrivals (mostly via MP) occurred between the Chalcolithic and the Roman Epoch (4.5-2 ky BP), when the innermost parts of the IP were colonized (Late Bronze). A second, likely anthropogenic, introduction acceleration took place in the Middle Ages (1.5 ky BP onward) using the MP and CP. Maximum cultivation and hemp retting activity was recorded during the Modern Ages (16 th -19 th centuries), coinciding with the increased demand of hemp fiber to supply the Spanish royal navy for imperial expansion and commerce. A potential link between Cannabis colonization/introduction bursts and climatic warmings has been observed that should be tested with future studies. Regional moisture variations seem to be less influential. Further efforts to enhance and improve the database used in this study are encouraged. The results of this paper should be compared with archaeological and historical evidence to clarify the role of human migrations and cultural changes in the historical biogeography of Cannabis in the IP.

Origin, early expansion, domestication and anthropogenic diffusion of Cannabis, with emphasis on Europe and the Iberian Peninsula

Article

Apr 2022
PERSPECT PLANT ECOL

Valentí Rull

Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection throughout history to create a wide array of varieties and biotypes for diverse uses, including fiber, food, biofuel, medicine and drugs. This paper briefly reviews the available literature on the taxonomy, evolutionary origin and domestication of this plant, as well as its worldwide dispersal, in both its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula. Today, it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originating in Europe and Asia, respectively, by allopatric differentiation after geographic isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographic evidence situates the Cannabis ancestor on the NE Tibetan Plateau during the mid-Oligocene. The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple Neolithic domestication centers situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses have suggested that wild Cannabis may have already been spread across Europe in the Pleistocene, and its domestication could have occurred during the European Copper/Bronze ages. According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have occurred only in postglacial times, and the earlier signs of cultivation date to the Early Medieval Ages. However, the palynological and archaeological evidence used to date is insufficient for a sound assessment, and the development of thorough Iberian databases to address further meta-analysis is essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.

Regional precipitation trends since 1500 CE, reconstructed from calcite sublayers of a varved Mediterranean lake record (Central Pyrenees)

Article

Full-text available

Feb 2022

The Mediterranean region is expected to be highly impacted by global warming, although the uncertainty of future scenarios, particularly about precipitation patterns remains quite large. To better predict shifts in its current climate system and to test models, more regional climate records are needed spanning longer than the instrumental period. Here we provide a high-resolution reconstruction of Autumn precipitation for the Central Pyrenees since 1500 CE based on calcite sublayer width from from Montcortès Lake (Central southern Pyrenees) varved sediments. The 500-yr calcite data series was detrended and calibrated with instrumental climate records by applying correlations and cross-correlations to regional precipitation anomalies. Highest relationships were obtained between a composite calcite series and autumn precipitation anomalies for the complete calibration period (1900–2002) and for the two halves of the full period. Applied statistical tests were significant, evidencing that the climatic signal could be reconstructed. The reconstructed precipitation anomalies show interdecadal shifts, and rainfall decrease within the coldest period of the LIA and during the second half of the 20th century, probably associated to current Global Warming. Neither increasing nor decreasing linear trends or periods of extreme precipitation events were identified. Our results are coherent with other palaeohydrological reconstructions for northern Iberian Peninsula. Correlations between the predicted autumn precipitation and the main teleconnections –NAO, ENSO and WEMO– were weak, although a potential relationship with the Atlantic Multidecadal Oscillation (AMO) pattern is suggested. The obtained reconstruction provides the first estimations of regional autumn precipitation shifts in the Central Pyrenees and is one of the few reconstructions that cover annual-to-century scale climate variability of precipitation in the Mediterranean region from the end of the Litte Ice Age (LIA) to the current period of Global Warming.

Origin, Early Dispersal, Domestication and Anthropogenic Diffusion of Cannabis, with Emphasis on Europe and the Iberian Peninsula

Preprint

Dec 2021

Valentí Rull

Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection throughout history to create a wide array of varieties and biotypes for diverse uses, including fibre, food, biofuel, medicine and drugs. This paper briefly reviews the available literature on the taxonomy, evolutionary origin and domestication of this plant, as well as its worldwide dispersal, in both its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula. Today, it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originating in Europe and Asia, respectively, by allopatric differentiation after geographic isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographic evidence situates the Cannabis ancestor on the NE Tibetan Plateau during the mid-Oligocene. The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple Neolithic domestication centres situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses have suggested that wild Cannabis may have already been spread across Europe in the Pleistocene, and its domestication could have occurred during the European Copper/Bronze ages. According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have occurred only in postglacial times, and the earlier signs of cultivation date to the Early Medieval Ages. However, the palynological and archaeological evidence used to date is insufficient for a sound assessment, and the development of thorough Iberian databases to address further meta-analysis is essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.

When and How Did Cannabis Reach Europe and the Iberian Peninsula?

Preprint

Nov 2021

Valentí Rull

Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection through history, to create a wide array of varieties and biotypes for a diversity or uses, including fiber, food, biofuel, medicine and drugs, among others. This paper briefly reviews the available literature on the taxonomy, the evolutionary origin and the domestication of this plant, as well as its worldwide dispersal, either in its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula, which is the main target of this study. Today it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originated in Europe and Asia, respectively, by allopatric differentiation after geographical isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographical evidence situate the Cannabis ancestor in the NE Tibetan Plateau during the Oligocene (ca. 28 Ma). The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple domestication centers, situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses suggest that wild Cannabis may have been spread across Europe already in the Pleistocene (ca. 1 Ma), and its domestication could have been occurred during the European Copper/Bronze ages (7-5 kyr BP). According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have been occurred only in post-glacial times (18.5-15 kyr BP) and the earlier signs of cultivation date to the Early Medieval Ages (ca. 600 CE). However, the palynological and archaeological evidence used to date is insufficient for a sound assessment and the development of thorough Iberian databases to address further meta-analysis are essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.

Regional Precipitation Trends Since 1500 Ce, Reconstructed from Calcite Sublayers of a Varved Mediterranean Lake Record (Central Pyrenees)

Preprint

Full-text available

Nov 2021

The Mediterranean is one of the regions of the world where human-induced climate warming is expected to have large impacts on water and environmental resources. To predict shifts in the current climate system, more regional climate records, including seasonal-to-century scale variability spanning longer than the instrumental periods, are needed. To help fill this gap, we provide a reconstruction of autumn precipitation variations for the Central Pyrenees range since 1500 Common Era (CE) using the varved sediments of Lake Montcortès. To assess the suitability of the calcite sublayer width of the sediments of this lake as a proxy for precipitation anomalies, we performed an analysis and smoothing of the temporal structure of the width series, calibration of the new series with the available instrumental climate records, calculation of a transfer function and testing and comparison of the reconstructed series against available empirical data.The prediction model was statistically robust and showed that the climatic signal was captured in the calcite sublayers. The reconstruction provides the first estimations of regional autumn precipitation shifts in the Central Pyrenees at annual resolution, since 1500 CE. Pronounced interdecadal shifts in precipitation were noticeable; no increasing nor decreasing linear trends or periods of extreme precipitation events were identified. The reconstructed precipitation anomalies suggest a decrease in rainfall during the coldest phase within the coldest period of the Little Ice Age and also during the 20th century, probably associated to current Global Warming. Correlations between autumn precipitation and the North Atlantic Oscillation, Western Mediterranean Oscillation and Southern Oscillation indices were weak to moderate. A potential relationship with the Atlantic Multidecadal Oscillation pattern is suggested. The reconstructed autumn precipitation trends are coherent with other palaeohydrological reconstructions in similar Mediterranean settings, and consistent at a regional level.

A unique Pyrenean varved record provides a detailed reconstruction of Mediterranean vegetation and land-use dynamics over the last three millennia

Article

Full-text available

Aug 2021
QUATERNARY SCI REV

The Pyrenean Lake Montcortès sediments hold the longest continuous and absolutely varve-dated record of the Mediterranean region, encompassing the last three millennia, from the Late Bronze Age to the present. The reconstruction of vegetation and landscape dynamics during this time period has advanced gradually, following the progress of absolute dating by varve counting, and has been progressively published and updated in a number of papers dealing with specific time intervals at different temporal resolutions. This paper synthesizes all these studies in a single composite paleoecological sequence constrained by a single age-depth varve model. The final resolution of this reconstruction is bidecadal, on average, but some periods have been resolved at quasidecadal (Middle Ages) and subdecadal (Modern Age to present) resolutions. The study is focused on the timing of anthropization and the further development of vegetation under climatic and anthropogenic drivers until the shaping of present landscapes. An additional advantage of Montcortès is that the local history of the Pallars region, where the lake is located, is well documented and can be easily correlated with the paleoecological record. Contrary to former interpretations of general landscape anthropization of the Pyrenees during the Middle Ages, the Montcortès catchment was irreversibly transformed by anthropic activities at the beginning of the Iron Age (ca. 750-650 BCE). From this point, the catchment underwent successive transformations due to varied human uses (fire, grazing, cereal cultivation, weed/ruderal plant expansions, hemp cultivation/retting), which have been related to the different cultural phases and sociopolitical changes documented in the local historical records. The regional forests, dominated by Pinus and Quercus, experienced four main clearance events (RD) during the Iron Age (RD1; ca. 300 BCE), the Roman Period (RD2; ca. 300 CE), the Middle Ages (RD3; ca. 1000 CE) and the Modern Age (RD4; ca. 1800 CE). The detailed trends of the last two deforestation events and their causes could be studied at a decadal resolution, which significantly improved interpretation quality in ecological terms. The potential effects of climatic changes and the eventual interactions with human activities on catchment vegetation and regional forests throughout the record have also been discussed. The Montcortès record has been compared with other records at local (Pyrenees), regional (Iberian Peninsula) and biome (Mediterranean) scales. Locally and regionally, anthropization times and further ecological trends showed significant heterogeneity according to elevation, biogeographical patterns and cultural trends. The most significant coincidence is an intensification of human pressure, as noted in forest clearing and extensive land use, during several phases of the Middle Ages. At the Mediterranean level, the Montcortès record emerges as a unique sequence for the western sector of this biome that should be complemented with similar archives from the central and eastern Mediterranean. The most promising candidates for such sequences are discussed on the basis of available Mediterranean varved records.

A unique Pyrenean varved record provides a detailed reconstruction of Mediterranean vegetation and land-use dynamics over the last three millennia

Preprint

May 2021

High mountain palaeoecology and palaeolimnology of Central Pyrenees, based on pollen and diatom analyses - PhD

Thesis

Nov 2018

Sandra Garcés Pastor

High-mountain ranges are suitable ecosystems for studying local environmental shifts driven by large-scale climate changes. Sedimentary records obtained from those regions contain information that allows to understand past environmental changes that would help to predict the influence of the ongoing climate warming. This thesis is focused in the palaeoecology and palaeolimnology of Central Pyrenees. In order to understand the ecosystem responses to past environmental changes and climate, we analysed several proxies from sedimentary sequences extracted from Bassa Nera pond. We combined biological indicators (pollen, diatoms, chrysophytes, non-pollen palynomorphs, microscopic charcoal particles, macroremains, tree-rings and DNA metabarcoding) and inorganic proxies (Loss-on-ignition and chemical elements) to assess the diverse questions proposed in this work. To infer vegetation shifts and aquatic changes during the past millennium, we analysed pollen and diatom at multidecadal resolution. A montane pollen ratio was introduced as a new palaeoecological indicator of altitudinal shifts in vegetation. Results emphasize the sensitivity of the montane ratio to detect upward migrations of deciduous forest and the presence of the montane belt close to Bassa Nera during the Medieval Climate Anomaly. Changes in aquatic taxa allowed to date the development of the peat bog in the coring site around AD 1565. Overall, the studied proxies suggest that Bassa Nera had a low-intensity human pressure and that people changed from farming in the Medieval Climate Anomaly to livestock in the Little Ice Age. To reconstruct the vegetation and lacustrine dynamics during the last 10,000 years we analyzed pollen, plant macroremains, charcoal, chemical elements and loss-on-ignition. The montane ratio was also applied to track altitudinal shifts and it was compared to the ice-rafted debris index. Results revealed upward shifts of deciduous forest and its presence in Bassa Nera from the onset of the Holocene until 4200 cal yr BP. The montane ratio showed a link between vegetation and North Atlantic influence, while changes in macroremains and aquatic taxa allowed the description of the transition from the initial pond to the present peatland. First anthropic pressures were grazing activities by 7300 cal yr BP, while cereal agriculture appeared around 5190 cal yr BP. The late Bronze Age, Roman Period and Middle Ages periods presented the highest human pressure. To assess the dynamics of subalpine forests of Central Pyrenees for the last 700 years, we compared the sedimentary pollen and montane ratio from Bassa Nera with nearby Pinus uncinata tree-rings. To study the climate-growth associations, we related the chronologies with instrumental meteorological records of the 1901-2010 period and with temperature reconstructions for the Pyrenees and Northern Hemisphere for the last 700 years. Few robust associations were found between any specific arboreal pollen taxa and tree-rings. However, a significant correlation was found between the montane ratio and the pine growth of nearby subalpine forests. Results suggest that tree-growth variability at high elevations is more constrained by low than by high temperatures, although a relaxation of this constrain in recent decades was also noted. To explore the eukaryotic communities of Bassa Nera, we performed a metabarcoding study of four different micro-habitats and five sedimentary depths using 18S and COI genetic markers. The sedimentary DNA from palaeoecological communities were compared to the modern communities and also to the environmental reconstruction from pollen and macroremains from the same record. Results show that even though 18S could amplify a broader group of organisms, the taxonomic resolution was lower than that obtained from COI and that the taxonomic assignment of the COI sequences yielded mostly metazoans. This first molecular approach has allowed to prove that the diversity of modern and past eukaryotic peat bog communities can be assessed using universal metabarcoding markers.

High-resolution (sub-decadal) pollen analysis of varved sediments from Lake Montcortès (south-central pre-Pyrenees): A fine-tuned record of landscape dynamics and human impact during the last 500 years

Article

Oct 2018
REV PALAEOBOT PALYNO

A high-resolution (average 6 years/sampling interval) palaeoenvironmental reconstruction using pollen, charcoal and non-pollen palynomorphswas carried out on annually laminated sediments of LakeMontcortès (southern Pyrenean flank). The results were combined with historical data to better understand landscape evolution and human interaction during the last 500 years. Our results show that human activities (cropping, livestock breeding and hemp cultivation and retting) have been the most important factors responsible for vegetation changes with highest intensity between 1530 and 1900 CE. By means of a sub-decadal study we have been able to evaluate short-lasting events at local and regional scales related to climate (heavy rainfall events and, high-land forest fluctuations) or to historical and well-dated and documented socio-economic events (i.e., crop promotions (hemp) or land abandonment-population emigration). The temporal extent (400 years) and continuity of Cannabis pollen peak have been confirmed, and new evidence of water quality changes, likely as a consequence of hempretting practices between the mid-17th to late 19th century, are provided. This is the first highresolution palaeoenvironmental study carried out in a varved lake on the Iberian Peninsula so far. With these data we hope to contribute to filling the gap in high-resolution palaeoenvironmental data.

Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula)

Article

Full-text available

Jan 2018
CLIM PAST

Holocene centennial-scale paleoenvironmental variability has been described in a multiproxy analysis (i.e., lithology, geochemistry, macrofossil, and microfossil analyses) of a paleoecological record from the Padul Basin in Sierra Nevada, southern Iberian Peninsula. This sequence covers a relevant time interval hitherto unreported in the studies of the Padul sedimentary sequence. The ∼ 4700-year record has preserved proxies of climate variability, with vegetation, lake levels, and sedimentological change during the Holocene in one of the most unique and southernmost wetlands in Europe. The progressive middle and late Holocene trend toward arid conditions identified by numerous authors in the western Mediterranean region, mostly related to a decrease in summer insolation, is also documented in this record; here it is also superimposed by centennial-scale variability in humidity. In turn, this record shows centennial-scale climate oscillations in temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The multiproxy Padul record first shows a transition from a relatively humid middle Holocene in the western Mediterranean region to more aridity from ∼ 4700 to ∼ 2800 cal yr BP. A relatively warm and humid period occurred between ∼ 2600 and ∼ 1600 cal yr BP, coinciding with persistent negative North Atlantic Oscillation (NAO) conditions and the historic Iberian–Roman Humid Period. Enhanced arid conditions, co-occurring with overall positive NAO conditions and increasing solar activity, are observed between ∼ 1550 and ∼ 450 cal yr BP (∼ 400 to ∼ 1400 CE) and colder and warmer conditions occurred during the Dark Ages and Medieval Climate Anomaly (MCA), respectively. Slightly wetter conditions took place during the end of the MCA and the first part of the Little Ice Age, which could be related to a change towards negative NAO conditions and minima in solar activity. Time series analysis performed from local (Botryococcus and total organic carbon) and regional (Mediterranean forest) signals helped us determining the relationship between southern Iberian climate evolution, atmospheric and oceanic dynamics, and solar activity. Our multiproxy record shows little evidence of human impact in the area until ∼ 1550 cal yr BP, when evidence of agriculture and livestock grazing occurs. Therefore, climate is the main forcing mechanism controlling environmental change in the area until relatively recently.

SEASONAL PATTERNS OF POLLEN SEDIMENTATION IN A PYRENEAN VARVED LAKE (MONTCORTÈS): APPLICATIONS TO HIGH-RESOLUTION PALEOECOLOGY

Poster

May 2017

Lakes with varved sediments are especially well suited for paleoecological reconstruction from annual to seasonal resolution. The interpretative power of these reconstructions relies on the availability of modern analogs with the same resolution. In this paper, we study the seasonal pollen sedimentation of a varved lake from the Central Pyrenees (Lake Montcortès) as a modern analog for the high-resolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a two-year period (from the Fall of 2013 to the Fall of 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus and Quercus, followed a clear seasonal pattern that peaked during the spring/summer (SS), coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed for most pollen types as significant amounts of pollen were found in the traps out of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition corresponding to spring/summer and fall-winter (FW). This pattern is consistent with the existing interpretation of the sedimentary varves: specifically, that the varves are formed by two-layer couplets that represent the same seasonality. It is concluded that pollen sedimentation in Lake Montcortès exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen and the relationships of the pollen to meteorological variables. Thus, varved sediments provide a powerful tool for paleoecological reconstruction at seasonal resolutions. This method could be useful not only for unraveling paleoenvironmental trends but also for identifying annual layers and therefore, dating the sediments, even in the absence of evident sedimentary laminations. A satisfactory explanation of pollen sedimentation lags will require more studies that examine internal lake dynamics (i.e. stratification vs. mixing) as well as pollen production and dispersal patterns.

Environmental and climate change in the southern Central Pyrenees since the Last Glacial Maximum: A view from the lake records

Article

Aug 2016
CATENA

Abstract In this contribution we compile and summarize the available paleo-environmental lacustrine data for the last 20,000 years from the southern Central Pyrenees (from west to east: El Portalet, Tramacastilla, Basa de la Mora, Estanya, Redon, Montcortès and Marcelino lakes) and present a new sequence from mid altitude (Holocene record of Lake Estanya). Multiproxy analyses of lake records have identified large vegetation and hydrological changes during last glacial, deglaciation and the Holocene periods at millennial, centennial and even decadal scales and documented their timing, intensity and varied nature. The review indicates that landscape dynamics in the Pyrenees have been greatly controlled by both long term and abrupt climate changes and, since the Middle Holocene, and particularly since Medieval times, by human activities as new transforming agent. Although high internal variability characterized every site, common temporal trends are evidenced, as well as a suggestive western–eastern gradient superimposed to the expected altitudinal one (highlands versus lowlands). Thus, the long-term Central Pyrenees environmental history presents a relatively high degree of internal coherence across space and provides some past scenarios of landscape-climate interactions to evaluate the expected impacts of current and future Global Change.

Transhumance and long-term deforestation in the subalpine belt of the central Spanish Pyrenees: An interdisciplinary approach

Article

Dec 2020
CATENA

A key problem in explaining the mountain landscapes of the Mediterranean region is the relationship between the development of transhumance (seasonal movement of livestock over long distances) and deforestation of the subalpine and upper montane belts at 1350–2200 m above sea level (m a.s.l.). We examined this relationship in the Central Southern Pyrenees using information from multiple proxies—archaeology, pollen analysis, lacustrine sedimentation patterns, historical documents, and geomorphology. Although there is evidence of forest clearing since the Neolithic, and we can infer the presence of shepherds and livestock in mountain areas based on archaeological sites and pollen analysis in some lacustrine records, there is no strong evidence for transhumance between the Ebro Depression and the Pyrenees during the Prehistory. Instead, we found evidence of transterminance (seasonal movement of livestock over short distances) during this time. Growth of human populations and the establishment of large-scale markets favored longer livestock movements during the Roman period, although we only have indirect information on this for other areas of the Iberian Peninsula and the Mediterranean region. A few documents indicate the occurrence of transhumance during the Early Middle Ages, whereas all other proxies indicate a general expansion of livestock and transhumance during the 12th and 13th centuries. This coincides with the Christian conquest of the Central Ebro Depression by the Aragon Kingdom, the organization of large wool markets in Western Europe, and the exemptions conferred by the kings of Aragon to herders in the city of Saragossa. This led to rapid deforestation, in that forests were rapidly logged or burned to expand the summer grasslands. During this period, written documents indicate many conflicts between people in the villages and valleys for control of summer grasslands, pollen analyses show a rapid decline of arboreal pollen, and geomorphology studies indicate greatly increased sedimentation rates following deforestation, suggesting intense erosion. Transhumance has declined since the end of the 18th century, and particularly throughout the 20th century, and this has led to tree re-colonization of less accessible and marginal areas. The hydrological and geomorphological consequences of these recent events are important topics for future studies.

Turia river delta and coastal barrier-lagoon of Valencia (Mediterranean coast of Spain): Geomorphological processes and global climate fluctuations since Iberian-Roman times

Article

Sep 2019
QUATERNARY SCI REV

Extensive drillings and 31 new C-14 datings were used to establish the geomorphological evolution of the Turia river delta and coastal barrier-lagoon system of Valencia (Spain) over the last three millennia. Integration of geomorphological, stratigraphic, malacological, sedimentological and geoarchaeological data enables us to relate river Turia avulsions and alluvial episodes to the development of coastal spits and barriers. Geomorphological changes in the study area may also be associated with global climate events, sea-level fluctuations or anthropogenic periods in the Turia catchment. Six phases may be differentiated: (1) a major early alluviation phase during the Iberian period, when the Turia river ran to the north of the coastal plain and sand spits closed the Valencia open lagoon environments, forming a permeable barrier (2800 BP to 2300 BP approximately); (2) an avulsion phase of the Turia river to the south at the end of the Roman period (4th century AD); (3) formation of a more advanced spit just behind the most recent barrier during the Late Antique Little Ice Age (LALIA, Visigothic period); (4) a flood period of high-magnitude with coarser sediments throughout the Medieval Climate Anomaly (MCA, 11th century AD), when La Punta meridional deltaic ridge developed, which can be related to beach ridge closing and marine isolation of the Valencia lagoon around the 12th century; (5) important river alluviation and growth of the recent coastal barrier favoured by Turia channel changes during the Middle Ages, in the early Little Ice Age (LIA); (6) rapid coastal progradation and decline in salinity in the Valencia lagoon between the Maunder sunspot minimum (MM) and the end of LIA.

Clim and Anthropog drivers of pollen succession IP 500 yr.pdf

Article

Full-text available

May 2023

Teresa Vegas-Vilarrúbia

A recent Cannabis pollen increase on the Iberian Pyrenees

Article

May 2023

The continuous, varved and absolutely dated sedimentary record of Lake Montcortès (Iberian Pyrenees) has provided evidence for a distinct and characteristic 20th century (1980s) increase in Cannabis pollen (20C) that persists today. This event was coeval with the geographical shift of the hemp production center in the Iberian Peninsula from east to northeast (where Lake Montcortès lies), which was accompanied by a significant production increase. This increasing trend was fostered by the renewed interest of the paper industry in hemp and was promoted by the onset of European Union subsidies to hemp cultivation. Illegal cannabis crops could have also contributed to the Cannabis pollen increase, but sound evidence is still lacking. These preliminary conclusions should be reinforced by increasing the resolution of the current palynological record and modeling the dispersal of Cannabis pollen around the Montcortès region. More similar high-resolution records are needed to verify the geographical extent of the 20C event. Additionally, Lake Montcortès varved sediments are proposed as a suitable candidate to characterize the onset of the "Anthropocene" epoch (mid-20th century), as currently defined by the Anthropocene Working Group.

Palaeoenvironmental Framing of the O Areal Roman Saltworks and Related Anthropogenic Activities in North-western Iberia

Article

May 2023

The NW Iberian city of Vigo contains buried structures of a Roman salinae that follow the ancient coastline. To investigate its environmental legacy, we studied two pedo-sedimentary profiles at the O Areal saltworks to reconstruct human activities during and after the salinae use, as well as framing them within the last two millennia of climate variability. The bottom layer consists of organic-rich sands, with marine palynomorphs, confined within the saltworks’ structures that operated during the Early Roman Empire, when the demand in fish-salted products increased and the salting industry fluorished on the Atlantic coast of Iberia. During the Late Roman Empire, salt production at the O Areal may have ended, coeval with the development of a marsh with hydro-hygrophyte vegetation and the salting industry demise. The Roman environment also experienced intense agropastoralism that triggered water eutrophication. After Roman times, a dune phase sealed the archaeologicl structures. The overall trend points to a shift from a marine to a terrestrial setting coeval to known periods of climate variability. Therefore, humans and climate impacted the coast during the last two millennia, including the very intense Roman-period saltworks, agriculture and livestock. Roman times climate would have also influenced the saltworks’ establishment and abandonment.

Bacterial phylogenetic markers in lake sediments provide direct evidence for historical hemp retting

Article

Full-text available

Oct 2022
QUATERNARY SCI REV

Documenting prehistoric and historical hemp retting for fiber extraction is important in the study of human uses of this iconic plant and its cultural implications. In paleoecology, hemp retting is usually inferred from indirect proxies, notably anomalously high percentages of Cannabis pollen in lake sediments , but some recent studies have also used specific molecular biomarkers (cannabinol, Cannabis DNA) as more straightforward evidence. Here we provide direct evidence of hemp retting by identifying phylogenetic signatures (16S rRNA genes) from pectinolytic bacteria actually responsible for the fermentation process that separates the fiber from the stalk, namely Bacillus, Clostridium, Escherichia, Massilia, Methylobacterium, Pseudomonas, Rhizobium and Rhodobacter. These analyses have been performed in the sediments from an Iberian lake previously considered as an important hemp retting site during the last five centuries, on the basis of Cannabis pollen abundances. The good match between biomarker and pollen evidence, in the context of the recent historical development of the hemp industry in Spain, can be useful to interpret paleoecological records from other similar lakes on the way toward a more regional view on the introduction, spreading, uses and associated cultural connotations of Cannabis in the Iberian Peninsula within European and Mediterranean contexts.

Climatic and Anthropogenic Drivers of Forest Succession in the Iberian Pyrenees during the Last 500 Years: A Statistical Approach

Article

Full-text available

Apr 2022

Anticipating future successional forest trends in the face of ongoing global change is an essential conservation target. Mountain forests are especially sensitive to environmental shifts, and their past responses to climatic and anthropogenic (external) drivers may provide a basis for improving predictions of future developments. This paper uses independent high-resolution palynological and paleoclimatic reconstructions to statistically analyze the long-term effects of external drivers on regional forest succession in the central Iberian Pyrenees during the last 500 years. The statistical methods used are Gaussian response analysis, cluster analysis, rate-of-change analysis, principal component analysis, and redundancy analysis. The dominant taxa of these forests (Quercus, Betula, Pinus) showed significant relationships with summer temperature, summer drought, and autumn precipitation. Immediate and delayed (by two or more decades) responses of these trees to climatic drivers were identified. Regional succession showed a closed path, starting at the end points around the attraction domain of pine-dominated forests. This trajectory was determined by a trend toward anthropogenic forest clearing (16th to 18th centuries) and a reverse trend of natural forest recovery (18th to 20th centuries). Forest clearing was due to burning, facilitated by drought, and was followed by the expansion of cropping and grazing lands. Forest recovery was fostered by reduced human pressure and rising temperatures. The statistical approach used in this work has unraveled ecological relationships that remained unnoticed in previous works and would be important for predicting future successional trends under changing climates. The reported response lags of individual taxa to climatic drivers may complicate the establishment of reliable ecological relationships and should be addressed in future studies.

Conifer Forest Dynamics in the Iberian Pyrenees during the Middle Ages

Article

Full-text available

Dec 2021

This study compares the Medieval (ca. 400–1500 CE; Common Era) dynamics of forests from low-mountain (Montcortès; ca. 1000 m a.s.l.) and high-mountain (Sant Maurici; 1900 m a.s.l.) areas of the Iberian Pyrenees, both of which experienced similar climatic forcing but different anthropogenic pressures. The main aim is to identify forest changes over time and associate them with the corresponding climatic and anthropogenic drivers (or synergies among them) to test how different forests at different elevations respond to external forcings. This can be useful to evaluate the hypothesis of general Pyrenean deforestation during the Middle Ages leading to present-day landscapes and to improve the background for forest conservation. The study uses the palynological analysis of lake sediments, historical documents and paleoecological reconstructions based on pollen-independent proxies. The two sites studied showed different forest trajectories. The Montcortès area was subjected to intense human pressure during regional deforestation up to a maximum of ca. 1000 CE. Further forest recovery took place until the end of the Middle Ages due to a change in forest management, including the abandonment of slash-and-burn practices. Climatic shifts indirectly influenced forest trends by regulating human migrations and the resulting shifts in the type and intensity of forest exploitation. The highland Sant Maurici forests exhibited a remarkably long-standing constancy and an exceptional resilience to climatic shifts, which were unable to affect forest extension and composition, and to local human pressure, from which they rapidly recovered. The Montcortès and Sant Maurici records did not follow the rule of an irreversible forest clearing during the Middle Ages leading to present-day landscapes. The present Montcortès landscape was shaped after a Medieval forest recovery, new Modern-Age deforestation and further forest recovery during the last centuries. The Sant Maurici forests remained apparently untouched since the Bronze Age and were never cleared during the Middle Ages. The relevance of these findings for forest conservation is briefly addressed, and the need for the development of more high-resolution studies on Pyrenean forest dynamics is highlighted.

Environmental evidence of Valencia Lagoon coastal barrier stabilization from 8500 BP to Present. Climate and eustatic variations

Article

Nov 2021
SCI TOTAL ENVIRON

The Albufera de Valencia is one of the largest lagoon in the Spanish Mediterranean. Two continuous borehole cores reaching depths of 8 and 14 m in the northern part of the lagoon underwent sedimentological, micropaleontological and biological study. The organic content was also analysed, and ¹⁴C radiometric dating and amino acid racemization were performed. Study of the content of benthic foraminifera and n-alkanes and alkanoic acids in the lagoon sedimentary record identified several periods. The core records showed seven different environments: alluvial; freshwater marsh; brackish marsh; brackish lagoon; brackish lagoon with marine connection, backbarrier flat, and backshore. These environments changed due to eight phases associated with the transgression and regression of the barrier system, which caused the shift from exposed environments as the backshore with washover, to the typical low-energy lagoon and marsh deposition. The paleoenvironmental evolution described above is interpreted as a response to global climate changes. The shift from an alluvial setting to a brackish lagoon is probably related to the late of Early Holocene sea level rise ending at the Holocene Climate Optimum, when the highest sea level was reached. The persistence of the brackish lagoon, with no marine connection, is probably synchronous with dry conditions in the area (Booth et al., 2005) at the time of Bond event 3 (i.e., 4.2 ka) in the North Atlantic region (Bond et al., 2001). Finally, the arrival of large amounts of sediment triggered the accretion of the barrier, also enhancing coastal progradation until the present day. These results allow an evaluation of the impact of anthropic action on the Valencia lagoon, especially since the eighteenth century, and a short- and medium-term projection of the consequences of present-day climate change.

Medieval Forest Dynamics in the Iberian Pyrenees: A Comparison Between Low- and High-mountain Areas

Preprint

Oct 2021

This paper compares the Medieval (ca. 400–1500 CE) dynamics of forests from low-mountain (Montcortès; ca. 1000 m a.s.l.) and high-mountain (Sant Maurici; 1900 m a.s.l.) areas of the Iberian Pyrenees, both of which experienced similar climatic forcing but different anthropogenic pressures. The main aim is to identify forest changes over time and associate them with the corresponding climatic and anthropogenic drivers (or synergies among them) to test how different forests at different elevations respond to external forcings. This could be useful to evaluate the hypothesis of general Pyrenean deforestation during the Middle Ages leading to present-day landscapes and to improve the background for forest conservation. The study uses palynological analysis of lake sediments, historical documents and paleoecological reconstructions based on pollen-independent proxies. The two sites studied showed different forest trajectories. The Montcortès area was subjected to intense human pressure during regional deforestation up to a maximum of ca. 1000 CE. Further forest recovery took place until the end of the Middle Ages due to a change in forest management, including the abandonment of slash-and-burn practices. Climatic shifts indirectly influenced forest trends by regulating human migrations and the resulting shifts in the type and intensity of forest exploitation. The highland Sant Maurici forests exhibited a remarkably long-standing constancy and an exceptional resilience to climatic shifts, which were unable to affect forest extension and composition, and to local human pressure, from which they rapidly recovered. The Montcortès and Sant Maurici records did not follow the rule of an irreversible forest clearing during the Middle Ages leading to present-day landscapes. The present Montcortès landscape was shaped after a Medieval forest recovery, a new Modern-Age deforestation and a further forest recovery during the last centuries. The Sant Maurici forests remained apparently untouched since the Bronze Age and were never cleared during the Middle Ages. The relevance of these findings for forest conservation is briefly addressed, and the need for the development of more high-resolution studies on Pyrenean forest dynamics is highlighted.

Actividad aluvial durante la Pequeña Edad del Hielo en Bardenas Reales de Navarra Alluvial activity during Little Ice Age in Bardenas Reales of Navarra

Article

Full-text available

Jan 2007

The geomorphology, sedimentology and pedology of the most recent alluvial unit (360±101 to 216±89 14 C cal BP) were studied in the Bardenas Reales Natural Park (Navarra province). This unit is either infilling former narrow channel sections, currently showing a terrace morphology (e.g. El Vedado), or insert on older morphopedosedimentary units with wide channel morphology (e.g. Salinero). It is composed of a sequence of slacked flood depositional units, centimetric in scale, with weak degree of soil development. The palaeoclimatic context is interpreted within a period of arid trend, characterised by a high hydroclimatic variability, and increase in the frequency of floods during Little Ice Age. Alluvial dynamics shows a high degree of geomorphic effectiveness as well as a very quick response to centennial scale climatic variability.

Rewilding and restoring cultural landscapes in Mediterranean mountains: Opportunities and challenges

Article

Dec 2020
LAND USE POLICY

Farmland abandonment and the decline of livestock activity in the Mediterranean mountains have resulted in dramatic landscape changes, including the generalized expansion of shrublands and forests, and the homogenization of the old cultural landscapes. This process has a variety of consequences from ecological, geomorphological and hydrological points of view, as well as from the perspectives of land management and public awareness. An intense debate currently surrounds the discussion and evaluation of rewilding (the process of passively allowing woody encroachment, as well as the reintroduction of large mammals) as an opportunity for enhancing biodiversity and restoring original landscapes after centuries of human activity versus ecological restoration (activities leading to the recovery of degraded ecosystems, including clearing and light human activity). There is no clear consensus regarding the best way to improve the ecological relationships and functioning within an ecosystem. Biodiversity and sustainability can be seen under different levels of human pressure and landscape transformation; total farmland abandonment is not always the best alternative, particularly when local inhabitants aim to sustain themselves using local resources. Many geographers and ecologists consider that extensive stockbreeding in a partially open landscape is a rational way to (i) improve landscape organization, (ii) increase flows and turnover within the ecosystems, (iii) increase the diversity of plants and animals that benefit from a relatively light human presence, and (iv) reduce wildfire risk. However, it has proven challenging for land managers and stockbreeders to clear the best old abandoned fields and “construct” a sustainable, balanced landscape that combines forests, shrublands and open lands. Private landowner involvement and support from the general public is crucial for both funding and the long-term maintenance of benefits. The best old fields should be cleared in the context of high-resolution knowledge of the topography, grassland characteristics, grassland cycles and livestock management. Such efforts are likely to be an excellent opportunity to introduce compatibility between light human activity and increases in biodiversity and sustainability for many marginal mountains, where land abandonment and general forest/shrub recovery are the inevitable tendencies. This paper examines some of the contrasting positions of the scientific community regarding the rewilding or ecological restoration of mountain landscapes, and briefly highlights some experiences in which intentional clearing of old abandoned fields has benefited stockbreeding, biodiversity, runoff generation and wildfire risks. Notably, we describe a sub-Mediterranean valley of the Iberian Range, Northern Spain, as an example. In the long term, we find that the intentional clearing of the best old fields allows the slow organization of a final landscape that will be more useful for local inhabitants, thereby helping to reverse human depopulation in these regions.

High-resolution patterns of palaeoenvironmental changes during the Little Ice Age and the Medieval Climate Anomaly in the northwestern Iberian Peninsula

Article

Full-text available

Jun 2020

A high resolution core (9.7 yr cm–1) from the Chao de Veiga Mol raised bog (NW Iberian Peninsula) was analysed to identify plant macrofossils, estimate peat humification and calculate hydroclimatic indices based on current bog species, with the overall aim of determining the climate conditions associated with evolution of the bog during the Medieval Climate Anomaly and the Little Ice Age. These proxies, together with historical and climate data, proved to be good indicators of the changes in bog surface wetness. Analysis of the core led to identification of 9 different periods: two corresponding to the so-called Medieval Climate Anomaly (930 to 1345 AD,1075–665 calibrated years before present [cal. yr BP]); four corresponding to the Little Ice Age (1345 to 1905 AD; 665–105 cal. yr BP); and three corresponding to the last century (1905 to 2000 AD). The findings revealed a generally dry climate that lasted until the 14th century, followed by a transition to a long period with a more humid, but characteristically very variable climate, which ended at the beginning of the 20th century and was followed by a rapid transition to more humid conditions and finally, a change to drier conditions. The Medieval Climate Anomaly was indicated by the abundance of dry-adapted mosses (Leucobryum glaucum, Hypnum cupressiforme) and characterized by warm dry conditions and high levels of peat humification, with alternating wet phases. The LIA period was dated by a large abundance of Sphagnum species (an indicator of wetness) and a gradual increase in the humification index. However, four different climate phases were differentiated in this period. High-resolution reconstruction of the evolution of the CVM bog and the multiproxy approach have together enabled a more detailed identification of climatic variations in this area, which are generally consistent with the global models, as well as better definition of the elusive climatic oscillations in the last millennium and confirmation of the importance of local modulation of global models. The study provides new information and a detailed chronology of climatic events that will help to refine local modulation of the climate evolution model in the still quite unexplored region of the NW Iberian Peninsula, a key area for understanding the paleoclimatic dynamics in SW Europe.

6700 years of diatom changes related to land use and climatic fluctuations in the Lake Aydat catchment (Auvergne, France): coupling with akinete cyanobacteria, pollen and non-pollen palynomorphs.

Article

Jan 2020
QUATERN INT

Nowadays Lake Aydat is an important site for tourism activities but blooms of cyanobacteria induced some restriction for aquatic activities by humans and their livestock. Thus, it was important to understand the lake's history as it should help in the development of restoration strategies to improve water quality in the future. Lake Aydat had a complex history affected by climatic changes and human influences. Two different sedimentary periods of deposition were observed (6700 ± 200–3180 ± 90, and 1770 ± 60 cal. BP – nowadays) separated by a mass wasting deposit. The lower unit was dominated by Stephanodiscus diatom species (S. medius, S. minutulus and S. parvus) and two Aulacoseira species (A. pusilla and A. subarctica) and the upper layer by Aulacoseira subarctica and its form recta along with Lindavia radiosa and a series of “Fragilariod” taxa. The eutrophic diatom species increase, associated with the lower layer, was most likely related to prehistorical human activities within the watershed (progressive change from a wooded landscape to an agricultural patchy landscape). The Middle Bronze Age degradation was noted as a period with a rise in planktonic and tychoplanktonic diatom species. The lower diatom zone in the upper unit marked the final transition to a domination of agricultural practices and high human pressure and a whole new set of environmental factors affecting the lake since 1750 cal. BP. Increased nutrient enrichment was observed and the Lindavia radiosa presence in the lake was associated with the beginning of hemp (Cannabis sativa) cultivation and an increase in agricultural pressure. High concentrations of cyanobacteria akinetes were associated with the final transition and the maximum of hemp cultivation, when the lake became very eutrophic. For future restoration strategies, improving the water quality will be a challenge as high concentrations of akinetes and nutrients are observed since the Antiquity in the lake.

Holocene history of Aleppo pine (Pinus halepensis Mill.) woodlands in the Ebro Basin (NE Spain): Climate-biased or human-induced?

Article

Apr 2020
REV PALAEOBOT PALYNO

This paper reviews the past distribution of Aleppo pine woodlands in the Ebro Basin, Northeastern Iberia, from the Mesolithic to Modern times based on wood charcoal data. The aim is to detail the chronological timing and the drivers explaining the long-term presence of Aleppo pine woodlands and associated thermophilous flora. The available charcoal data support the early spread of Pinus halepensis during the Mesolithic (ca. 10.000–9600 cal BP) accompanied by Mediterranean trees and shrubs like Quercus sp. evergreen, Juniperus sp., Arbutus unedo, Pistacia lentiscus, Rhamnus/Phillyrea, Cistaceae, and Rosmarinus officinalis, as a local response to global climate change in the Early Holocene. During the arrival and the propagation of the Neolithic culture (ca. 7500–5500 cal BP), anthracological records, as well as regional palynological sequences, demonstrate the progressive replacement of an conifer-dominated open parkland by both Quercus sp. deciduous and evergreen woodlands in response to the Middle Holocene rise in temperature and humidity. This evidence, however, converges with the general idea that the presence and the spread of Pinus halepensis and associated scrubland have usually been attributed to the onset of landscape anthropization. The frequency of xero-thermophilous open scrubland and the use of Aleppo pine for fuel and woodcrafting progressively increased during the Bronze and Iron Ages, and especially in Ibero-Roman and Medieval/Islamic times, when the vegetation landscape in the Middle Ebro Basin was largely deforested as a consequence of increasing demographic pressure, grazing and the establishment of proto-urban centers.

Multi proxy analysis for reconstructing the late Holocene evolution of a Mediterranean Coastal Lagoon: Environmental variables within foraminiferal assemblages

Article

Dec 2019
CATENA

This study reconstructs the evolution of foraminiferal assemblages and the environmental variables (type of substrate, content in calcium carbonate and content in organic matter) in the Valencia lagoon (western Mediterranean) in response to changes in the late Holocene. In this area of low tidal range, several multiproxy analyses were carried out to determine which environmental variables influence the distribution of the fossil assemblage, and its association with global, regional or local climatic phenomena. The statistical results show that in environments with higher exposure to marine conditions, the calcium carbonate content is the dominant factor, whereas in more restricted environments the type of substrate (grain size) is determinant. The micropaleontological content reveals the evolution from a saline paleoenvironment with a clear marine influence towards the hyposaline or freshwater conditions, recorded at the top. Three phases were identified in the evolution of this area from 2800 cal yr BP to the present. A brackish lagoon with marine connection at the base, followed by a deposit of brackish lagoon (1232 ± 74 cal yr BP − 791 ± 104 cal yr BP), culminating in a brackish marsh (791 ± 104 cal yr BP to present), interpreted as the definitive closure process of the lagoon, favored by the coastal progradation processes related with an extraordinary input of sediments. These findings reflect the climatic variability of the Medieval Climate Optimum (MCO) (1.05 and 0.65 kcal BP) and the migration of the river Turia mouth, which favored the coastal progradation processes. The flood events registered at this phase, may have coincided with changes in the landscape and greater anthropic influence at the end of the LIA, 150 cal yr BP. Coastal processes are mainly responsible for the evolution of this area during phase I, while the influence of fluvial processes is significant towards the top, especially in phase III.

A study of late Holocene local vegetation dynamics and responses to land use changes in an ancient charcoal making woodland in the central Pyrenees (Ariège, France), using pedoanthracology

Article

Full-text available

Mar 2020
VEG HIST ARCHAEOBOT

Human activities have profoundly transformed mountain woodland landscapes, particularly in the Pyrenees where they have intensified and diversified since the Bronze Age. Quantification of the role played by past practices with regard to woodland cover is critical for accurate assessment of how ongoing global environmental change may affect its dynamics in the future. A local study was made of charcoal remains from an ancient charcoal-making woodland (ca. 30 ha), the forêt de Bernadouze, located on a north-facing slope in the Vicdessos valley in the French central Pyrenees. This valley is well known as having had a long history of human influence related to pastoralism, iron ore mining and smelting. A total of 1,695 charcoal pieces from soils in three sampling pits were extracted, identified, quantified and dated in order to identify tree canopy openings and patterns of change in the woodland driven by past human uses. The results provide new and original insights regarding 1, the past higher biodiversity and the ancient character of the forêt de Bernadouze, 2, the dynamics and history of the main trees and 3, successive phases of human activity. We show that the current woodland has resulted from several millennia of human activities such as pasturing and use of the wood for making charcoal. From the Bronze Age, humans have progressively transformed a natural fir-dominated woodland into a managed beech-dominated one, and caused the elimination of Taxus baccata L. (yew).

Late Holocene local-scale vegetation dynamics and land-use changes in an ancient charcoal making forest of the upper Vicdessos Valley (central Pyrenees, France): a pedoanthracological approach

Article

Apr 2019
VEG HIST ARCHAEOBOT

Human activities have profoundly transformed mountain forest landscapes, particularly in the Pyrenees where they have intensified and diversified since the Bronze Age. Quantification of the role played by past practices with regard to forest cover is critical for accurate assessment of how ongoing global change may affect their dynamics in the future. A small-scale pedoanthracological approach was implemented within an ancient charcoal-making forest, the Bernadouze forest located on a north-facing slope of the Vicdessos valley in the French Central Pyrenees. This valley is well known as having a long anthropogenic pressure history related to pastoralism, iron mining and metallurgy. Charcoals from soils (3 sampling points, n=1695) were identified, quantified and dated in order to identify canopy openings and pattern of change in the forest driven by past anthropogenic uses. Results provided new original insights regarding the (i) past higher biodiversity and the ancientness of the Bernadouze forest, (ii) the dynamics and history of the main forest species and (iii) successive anthropogenic phases and human uses. We show that the current forest resulted from several millennium of forestry practices (sylvo-pastoralism and logging for charcoal-making). From the Bronze Age, humans have progressively transformed an old-growth fir-dominated forest into a beech-dominated production forest and induced the elimination of yew (Taxus baccata L.).

A Late Antique Vegetation History of the Western Mediterranean in Context

Chapter

Full-text available

Feb 2019

Evolution of a salt-affected lake under changing environmental conditions in Danube-Tisza interfluve

Article

Full-text available

Jan 2019

There are many shallow, environmentally sensitive salt-affected lakes in the Danube-Tisza Interfluve, Hungary. Because of long-term tendencies in regional and local hydrological and meteorological conditions (e.g. channelization, precipitation extremities, consecutive droughts) significant changes occurred in the state of these shallow lakes (or soda pans) in the last decades. In the example of Lake Szappanos the changes were studied that have taken place over the last three decades, such as the quality of surface water, groundwater and soil condition, transformation of vegetation, in 2014/2015 - repeating a survey in 1982. In the observed points, the average depth of groundwater level slightly dropped, away from the lake the differences became more pronounced, while the extension of the lake surface decreased. The soluble salt content of the groundwater decreased by one order of magnitude. The saline groundwater lies deeper, getting to lose its role as the source of salt. The rainfed near-surface water can act as a "freshwater cushion", which results in freshwater-like conditions, accompanied by changes in the vegetation. The "desalinization" process can be reversed to some extent and the Smaroglay's (1939) lake-evolutionary stages ("white" to "black" lake toward freshwater marsh) could be interchangeable in both directions by changing the influencing factors.

Holocene sea level and climate interactions on wet dune slack evolution in SW Portugal: A model for future scenarios?

Article

Full-text available

Oct 2018

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr−1, between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands’ seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat’s resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes.

BOSQUES EN MOVIMIENTO. CASUÍSTICAS EN LA PENÍNSULA IBÉRICA DURANTE EL CUATERNARIO TARDÍO

Article

Full-text available

Jan 2018

Resumen. Este artículo pretende una revisión crítica de los datos palinológicos del Cuaternario ibérico con particular atención al Pleistoceno Tardío y Holoceno. Se analizan aspectos relacionados con la ciclicidad climático astronómica y su influencia sobre la cubierta vegetal, los reservorios de fitodiversidad durante los estadiales, la colonización tardiglacial y holocena y el posible efecto de la acción antrópica sobre la dinámica forestal a partir del Holoceno Medio. Se comparan las zonas de influencia atlántica con las áreas de clima continental y la vertiente mediterránea. La perspectiva no es, en cualquier caso, climaticista sino histórico contingente. Palabras clave. Palinología. Paleoecología. Pleistoceno. Holoceno. España. Portugal. Quercus. Pinus. Abstract. FORESTS IN MOVEMENT. CASUÍSTICS IN THE IBERIAN PENINSULA DURING THE LATE QUATERNARY. This paper brings a critical revision of the palynological data from the Iberian Quaternary with special attention to the Late Pleistocene and Holocene. The climatic, astrononomically controlled cyclicity is analysed in the context of vegetational developments, and a discussion is provided on the phytodiversity reservoirs during glacial stadials, the Tardiglacial and Holocene forest colonisation, and the effects of anthropogenic activities on forest dynamics from Mid–Holocene onwards. Atlantic and Mediterranean regions are compared. The perspective here is not climaticist, but historical contingent. Key words. Palynology. Palaeoecology. Pleistocene. Holocene. España. Portugal. Quercus. Pinus.

Millennial-scale cyclical environment and climate variability during the Holocene in the western Mediterranean region deduced from a new multi-proxy analysis from the Padul record (Sierra Nevada, Spain)

Article

Jun 2018
GLOBAL PLANET CHANGE

The Little Ice Age in Iberian mountains

Article

Nov 2017
EARTH-SCI REV

The Little Ice Age (LIA) is known as one of the coldest stages of the Holocene. Most records from the Northern Hemisphere show evidence of significantly colder conditions during the LIA, which in some cases had substantial socio-economic consequences. In this study we investigated the magnitude and timing of climate variability during the LIA in the mountains of the Iberian Peninsula, based on a wide range of natural records (including from glacial, periglacial, and lacustrine/peatland areas; fluvial/alluvial deposits; speleothems; and tree rings), historical documents, and early instrument data. The onset of the LIA commenced in approximately CE 1300, and cold conditions with alternating moisture regimes persisted until approximately CE 1850; the environmental responses ranged from rapid (e.g. tree rings) to delayed (e.g. glaciers). The colder climate of the LIA was accompanied by severe droughts, floods, and cold/heat waves that showed significant spatio-temporal variation across the Iberian mountains. Several phases within the LIA have been detected, including (a) 1300–1480: increasing cooling with moderate climate oscillations; (b) 1480–1570: relatively warmer conditions; (c) 1570–1620: gradual cooling; (d) 1620–1715: coldest climate period of the LIA, particularly during the Maunder Minimum, with temperatures approximately 2 °C below those at present; (e) 1715–1760: warmer temperatures and a low frequency of extreme events; (f) 1760–1800: climate deterioration and more climate extremes (i.e. cold and heat waves, floods and droughts); (g) 1800–1850: highly variable climate conditions alternating with stability (1800–1815), extreme events (1815–1835), and a slight trend of warming associated with intense hydrometeorological events (1835–1850); (h) since 1850: a gradual staggered increase in temperature of approximately 1 °C. Post-LIA warming has led to substantial changes in geo-ecological dynamics, mainly through shrinking of the spatial domain affected by cold climate processes.

Un acercamiento a la vida cotidiana en los primeros años del Islam en el norte de la Península Ibérica: Una cocina del siglo VIII d.C. en El Pueyo (Los Bañales, Uncastillo, Zaragoza). I. Estudio arqueológico, fragmentos metálicos y óseos/An approach to the daily life in the early years of islam in the north of the Iberian Peninsula. An eighth century kitchen in El Pueyo (Los Bañales, Uncastillo). I. Archaeological study, metal and bone fragments.

Article

Full-text available

Dec 2016

El objetivo del presente trabajo es dar a conocer los resultados de la excavación de una cocina datada en la segunda mitad del siglo viii d.C. en El Pueyo (Los Bañales, Uncastillo). La calidad y cantidad del material recuperado permiten realizar un acercamiento de primera mano a la vida cotidiana de la sociedad en un momento muy poco conocido, centrándonos en este artículo en la descripción morfológica del espacio y el análisis de los restos de fauna y metálicos.

A six thousand year record of climate and land-use change from Mediterranean seagrass mats

Article

Full-text available

Feb 2017
J ECOL

The Mediterranean seagrass Posidonia oceanica maintains a biodiverse ecosystem and it is a world‐wide important carbon sink. It grows for millennia, accumulating organic‐rich soils (mats) beneath the meadows. This marine habitat is protected by the European Union; however, it is declining rapidly due to coastal development. Understanding its response to disturbances could inform habitat restoration, but many environmental impacts predate monitoring programs (<50 years). This research explores the palaeoecological potential of Posidonia mats to reconstruct six thousand years of environmental change that could have affected Posidonia meadows and, in turn, left an imprint on the mats. Palynological, microcharcoal, magnetic susceptibility and glomalin‐related soil protein ( GRSP ) analyses on Posidonia mats enabled us to detect climate‐ and human‐induced environmental processes impacting on the seagrass during the Late Holocene. The pollen and microcharcoal records reconstructed anthropogenic disturbances attributed to agriculture. The record of GRSP shows that agrarian activities affected continental soil quality. Changes in magnetic susceptibility reveal that enhanced soil erosion was caused by both climate (major flooding events in the NW Mediterranean) and humans (cultivation) which impacted on the Posidonia mat. Finally, increased human impact is linked to eutrophication of coastal waters since Roman‐Medieval times. Synthesis . This study shows that climate and land‐use changes in the western Mediterranean resulted in enhanced loadings of terrigenous material to the coastal zone since the Late Holocene, likely disturbing the Posidonia meadows and their mat carbon accumulation dynamics. Under the current global change scenario in which CO 2 emissions are projected to increase, restoring carbon sinks is a priority. Seagrass habitat restoration should consider not only the coastal perturbations, but also the continental ones at a catchment scale to preserve the socio‐economic ecosystem services provided by seagrasses.

Variabilidad climática y antropización del espacio en la Meseta durante los últimos 3000 años: estudio paleoambiental de las lagunas de Somolinos (1240m, Sierra de Pela, Guadalajara)

Conference Paper

Full-text available

Jan 2008

Middle Ages

Chapter

May 2024

The forest recovery of the Migration Period (376–568 CE) ended in the Visigothic epoch, when a long-term deforestation trend lasting ~4 centuries started, reaching minimum forest cover values (>50% and almost 70% less tree pollen than modern and Late Bronze values, respectively) at the beginning of Pallars independence in the tenth century. Cereal cultivation was still the main activity, but grazing and hemp cultivation for domestic purposes were increasing. The MCA (Medieval Climate Anomaly) warming could have contributed to an upward shift in vegetation belts, as manifested in the regional decrease in montane conifer forests and pastures, which may have migrated to higher elevations. Forest opening remained fairly stable (30–40% tree pollen) during most of the Pallars County phase; when wood/charcoal extraction increased, slash-and-burn practices decreased, and cultivation and grazing continued. The prolonged MCA warmer climates may have favored the decline of montane and submontane forests, which were replaced by lower-elevation Mediterranean forests. A significant expansion of lowland olive groves was recorded since 1290 CE, probably linked to the downslope migration of human populations fostered by the onset of the Little Ice Age (LIA) cold reversal. Forest recovery started by 1350 CE due to the substantial depopulation of the Pallars region as a consequence of the ending Medieval crisis.

Modern and Contemporary Times

Chapter

May 2024

The forest recovery initiated with the final Medieval crisis ended soon (1500 CE), when a third large-scale deforestation began, linked to a significant regional population increase. Maximum deforestation (~50% and >60% less tree pollen than present and Late-Bronze values) occurred by the middle eighteenth century, coinciding with the maximum of iron forges, which required abundant carbon supplies. Minimum forest cover also coincided with an abrupt increase in large-scale hemp retting, which was the main activity around the lake between the sixteenth and nineteenth centuries, to provide fiber for sails and ropes to the royal navy, which was crucial for the worldwide expansion of the Spanish Empire. Forest recovery started in the transition to Contemporary times (late-eighteenth century) and continued until the present, with a minor and brief retraction during the Industrial Revolution (mid-late nineteenth century). Hemp retting was abandoned by 1850 CE, coinciding with the end of the Spanish Empire and the dismantling of the royal navy. This was also the onset of a major regional depopulation of the Pallars region due to the massive emigration to lowland industrialized cities, notably Barcelona and its surroundings. Hemp cultivation in the southern Montcortès lowlands was revived in the 1980s to provide pulp for the paper industry and declined again in the 2000s.

Challenging reconstruction of the plurimillennial morphodynamics of hybrid urban deltas: Trajectory from a wave-dominated delta to a human-dominated delta in the Western Mediterranean area

Article

Full-text available

Mar 2024
GEOMORPHOLOGY

The reconstruction of the human impacts on the morphodynamics of river deltas in the long term is challenging. The ternary diagram of Galloway (1975) used to classify morphodynamics of deltas does not include direct human influence which is now affecting most of the deltas of the world. The study of human-dominated deltas requires specific approaches and consideration of human processes and morphologies in interaction with more commonly studied natural processes and morphologies. This study demonstrates how to combine different datasets from natural and social sciences to reconstruct long term temporal trajectories of hybrid urban deltas. The Francolí delta, associated with the UNESCO city of Tarragona, offers a perfect case study to identify the different steps of a wave-dominated delta leading to a human-dominated delta over a long-term perspective. Tarragona emerged in the 1st millennium BCE and became a significant port city in the Roman period. This study identifies the evidence of a semi-protected harbour built 2000 years ago that initiates the evolution of a hybrid urban delta towards a human-dominated delta. Until the end 19th c. CE, cyclical changes at the river mouth are observed due to natural fluvial and coastal dynamics while progradation stages are partly affected by anthropogenic structures over time. The 19th c. CE is a major turning point. Morphodynamics controlled by anthropogenic factors strongly increase while fluvial and coastal sedimentation is partly erased by dredgings. The systematic approach proposed for the Francolí delta can be standardised and applied to other hybrid urban deltas allowing better comparison between urbanised deltas.

An ecological perspective for analysing rural depopulation and abandonment

Article

Full-text available

Feb 2024

Population loss in rural areas is rapidly increasing in high‐income countries, raising concerns and debate, given its socio‐economic consequences. Despite the evident environmental dimension of the phenomenon, ecological knowledge has been neglected in the analysis of actions aiming to reverse rural depopulation. Particularly, cultural landscapes reflect memories of ecological processes that have configured current patterns of biodiversity and ecosystem services. Based on ecological principles, we present a conceptual procedure to assess the behaviour of social–ecological systems subjected to depopulation, projecting their expected trajectories through time within a framework defined jointly by demographic and environmental–ecological dimensions (in our case, biodiversity, carbon storage, pollution control, water resources and soil conservation). We applied this procedure to various alternative interventions designed to confront depopulation in Spain: (1) non‐intervention, (2) maintenance of the historical landscape configuration, (3) active conservation, (4) extensive, sustainable land use and (5) intensified land use. We conclude that extensive, sustainable land use better optimizes criteria of demographic consolidation, environmental impact, resilience and implementation of actions confronting depopulation. We highlight the need to incorporate ecological knowledge into the assessment and application of actions confronting rural depopulation. Read the free Plain Language Summary for this article on the Journal blog.

Paleoenvironmental variability and anthropic influence during the last 7300 years in the western Mediterranean based on the pollen record of Cartagena Bay, SE Spain

Article

Jan 2022
PALAEOGEOGR PALAEOCL

In this paper, we conduct a palynological analysis of a high-resolution Holocene record from Cartagena Bay, southeast of the Iberian Peninsula, to establish paleoenvironmental variability of coastal areas in the western Mediterranean region at a centennial-scale over the last 7300 years. Statistical analysis of four palynozones allows reconstruction of paleotemperature and paleohumidity conditions. Pinus, steppic, xerophilous, and Mediterranean taxa persisted continuously through the record, and only during periods of increased humidity did deciduous and Mediterranean taxa expand (Zones II, subzone IIIb). Cooler and dry conditions favored the development of Cupressaceae and scrubs between 7300 and 7000 yr cal BP. The mid-Holocene (Northgrippian) mesophytic optimum took place between 6800 and 4000 yr cal BP during which time a Mediterranean climate was present and open forest developed, predominantly consisting of Mediterranean taxa and deciduous trees. The gradual rise in aridity in the Meghalayan (4000–1700 yr cal BP) led to Mediterranean forest being replaced by steppic and xerophilous vegetation, a change related mostly to a decrease in summer insolation, with superimposed centennial-scale variability in humidity. In parallel with forest degradation caused by increasing aridity, the record shows marked evidence of human influence since 4000 yr cal BP, which accelerated the progression of open landscapes from the Chalcolithic onwards, this change being especially marked during the Roman period. Significant denudation of the landscape can be attributed to the use of fire, as well as due to agriculture and grazing, with a major contributor being intense metallurgical and mining activity in the area. The Cartagena Bay record reported herein shows centennial-scale oscillations in humidity and temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The alternation of persistent North Atlantic Oscillation modes is likely to have played a key role in regulating humid–arid periods.

A spatiotemporal gradient in the anthropization of Pyrenean landscapes. Preliminary report

Article

Apr 2021
QUATERNARY SCI REV

A preliminary analysis of the timing of landscape anthropization in the southern-central Pyrenees shows the occurrence of an elevational gradient from the Bronze Age (basal belts) to the Middle Ages (alpine belts). This relationship is statistically significant and suggests an average anthropization rate of 40 m in elevation per century. The elevational gradient is most clear between the Bronze Age and the Roman occupation, suggesting a progressive upward anthropization trend from the south with the likely involvement of Iberian cultures. During the Middle Ages, a massive anthropization pattern of subalpine/alpine areas is observed; this pattern is chronologically consistent with the incursion of northern cultures crossing the Pyrenees and the development of extensive high-mountain pastoralism and horizontal transhumance. In general, the progression of upward anthropization has occurred during warm climatic phases. Further work is needed to confirm these observations, especially in areas with few available paleoecological studies, notably the basal and montane belts. It could be interesting to develop similar studies of other Pyrenean regions and other mountain ranges.

A Late Antique Vegetation History of the Western Mediterranean in Context

Article

Jan 2018

Fossil pollen records from 70 sites with reliable chronologies and high-resolution data in the western Mediterranean, were synthesised to document Late Holocene vegetation and climate change. The key elements of vegetation dynamics and landscape construction during Late Antiquity are clear in the light of the fossil pollen records. These are: fire events (natural or anthropogenically induced); grazing activities in high-mountain areas; agriculture; arboriculture; and human settlement in the lowlands. In terms of anthropogenic pressure, the differences recorded between highlands and lowlands suggest an imbalance in land use. Such practices were related to three main types of activities: wood exploitation and management, cultivation, and pastoralism. In lowland areas there seems to be some synchronism in vegetation dynamics during the late antique period, since most of the territories of the western Mediterranean had been deforested by the Early Roman period. However, in mountainous regions, pollen records document a clear asynchrony.

Cambio climático y cultural en la Península Ibérica: una perspectiva geohistórica y paleoambiental.

Book

Full-text available

Dec 2017

Seminari d’Estudis i Recerques Prehistòriques (SERP).

Article

Full-text available

Jan 2015

Peptization and sieving for palynological purposes

Article

Full-text available

Jan 1989

Cambios ambientales durante el Holoceno en el Valle Medio del Ebro: Sus implicaciones arqueológicas

Article

Full-text available

Jan 1991

Resumen. A traves de un estudio interdisciplinar desarrollado en los ultimos afios por un equipo de investigacion compuesto por palinólogos, geomorfologos y arquelogos, Se pretenden conocer los cambios ambientales durante el Holoceno en el Valle Medlo del Ebro. Estos cambios medioambientales permiten examinar la relacion entre Ia historia climatica, Ia actividad humana y los procesos sedimentarios sobre una amplia base temporal y espacial. De forma preliminar, y en espera de resultados de analisis y de ampliacion del estudio, Se concluye que los sistemas lago-salinos (saladas) y fluviales del area de estudio proporcionan secuencias sedimentarias apropiadas para una reconslruccidn paleoambiental de Ia zona. Las variaciones clirnáticas y ambientales observadas en los distintos registros debieron includir de forma importante en Ia ocupación humana de esa zona habiendose observado importantes variaciones a lo largo del tiempo en los sectores más intensamente prospectados (area endorreica de Alcafiiz). Se considera necesario, por tanto, aumentar considerablemente los registos arqueológicos, los distintos tipos de anãlisis y clarificar Ia interaccion entre Ia actividad humana y los cambios climaticos para Ilegar a conclusiones mas firmes

Man and vegetation in the pollen diagrams from Wolin Island (NW Poland)

Article

Full-text available

Jan 1992

Małgorzata Latałowa

Pollen, charcoal and ash content data complemented by 26 14C dates from three small (4-5 ha) basins on Wolin Island (NW Poland) enabled a detailed chronological reconstruction of human impact on vegetation during the last 8000 yr. Locally, woodland was already actively changed in the Mesolithic. Animal husbandry and cereal cultivation are probably initiated by the people representing the Ertebolle culture. The first ulmus decline is radiocarbon dated in two profiles at c5800 BP and seems to be caused mainly by human activity. In the neolithic and Bronze Age coppicing changed the forest structure, animal husbandry was the main form of farming at that time. Cultivation increased in importance in the Lusatian culture and in the Iron Age, but the considerable extension of arable land did not take place until the early Middle Ages. -from Author

Poblamiento y organización del espacio La Tarraconense pirenaica en el siglo VI

Article

Full-text available

Jan 2003

Karstification without carbonic acid: Bedrock dissolution by gypsum-driven dedolomitization

Article

Full-text available

Nov 1994
GEOLOGY

Aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer. Gypsum dissolution drives the precipitation of calcite, thus consuming carbonate ions released by dolomite. Lake Banyoles, in northeastern Spain, is a karst lake supplied by sublacustrine springs, and karstic collapse is occurring in the immediate vicinity of the lake. Lake water is dominated by Mg-Ca and SO4-HCO3, and is supersaturated with calcite that is actively accumulating in lake sediments. Water chemistry, sulfur isotope composition, local stratigraphy, and mass-balance modelling suggest that the primary karst-forming process at at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. Gypsum-driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil-generated carbonic acid.

Remarques paleoecologiques a propos de quelques palynomorphes non-polliniques provenant de sediments quaternaires en France

Article

Full-text available

Neorhabdocoela oocytes - Palaeoecological indicators found in pollen preparations from Holocene freshwater lake sediments

Article

Full-text available

Mar 1996
REV PALAEOBOT PALYNO

Jean Nicolas Haas

Oocytes produced by aquatic flatworms of the order Neorhabdocoela are not destroyed by the chemical treatment of freshwater lake sediments for pollen analytical purposes. Until now these oocytes have commonly been ignored by palynologists. We present here the first detailed study of Neorhabdocoela oocytes from Central Europe, and discuss their palaeoecological significance. By analysing pollen slides from the Boreal and Atlantic periods of northeast Switzerland, oocytes of 14 different species and types were identified (of the 45 central European Neorhabdocoela species extant today). Because of their specificity and restriction to certain habitats, Neorhabdocoela oocytes allow the reconstruction of former freshwater quality and lake productivity, and may help us to understand temperature and hydrological changes during the Quaternary.

Responses of a Saline Lake Ecosystem in a Semiarid Region to Irrigation and Climate Variability

Article

Full-text available

Sep 2000

To adequately manage the fragile and changing environments of semiarid regions it is essential to disentangle human from climate or other environmental impacts over longer timescales than human memory. We investigated sediment cores from Salada Chiprana, a saline lake in the central Ebro basin in Spain, using pollen, charcoal, sedimentological, geochemical and radiometric dating techniques. The sequence indicates a rapid evolution from an ephemeral playa lake during the Late Holocene to a permanent saline lake a few centuries ago. The limnological evolution correlates with changes in agricultural practices and provides evidence of the strong impact of irrigation on the lake's hydrological balance from the XVth century. The work demonstrates that the Salada Chiprana, the only permanent, relatively deep, hypersaline lake in Spain has been created by a long history of human interaction with the landscape.

Responses of a Saline Lake Ecosystem in a Semiarid Region to Irrigation and Climate Variability: The History of Salada Chiprana, Central Ebro Basin, Spain

Article

Full-text available

Sep 2000

The long history of Cannabis and its cultivation by Romans in Central Italy (pollen records from Lago Albano and Lago di Nemi)

Article

Full-text available

Sep 2002

The cores of Albano and Nemi lakes, near Rome, were studied within the EC funded PALICLAS project and provided high resolution records of the Lateglacial and Holocene. Pollen evidence of increasing human influence on vegetation was recorded in the Holocene in both diagrams, and the Cannabis (hemp) curve was one of the major signs. In this paper we present unambiguous pollen evidence of the cultivation of hemp in Central Italy by Romans in the framework of the Cannabaceae records. The oldest records of Cannabis and Humulus (hop) dated to the Lateglacial. Hop pollen rose during the Middle Holocene, while hemp pollen became more abundant from ca.3000 cal B.P. onwards. The highest earliest hemp peak (21%) dated to the I cent. A.D. This ‘Cannabis-phase’, i.e. the abrupt rise of hemp pollen soon after the rise of cultivated trees (Castanea, Juglans and Olea) was associated with the increase in cereals and ruderal plants. This unambiguous proof of cultivation by Romans around 2000 B.P. occurred within a long lasting pre-Roman presence of hemp in the area, which was natural and possibly also anthropic. Subsequent clear episodes of cultivation were found in the Medieval Ages.

Archaeological and Palaeoecological Aspects of a Medieval House Terp in a Reclaimed Raised Bog Area in North Holland.

Article

Full-text available

Jan 2002
J ARCHAEOL SCI

The village of Oostzaan is situated in a region covered by raised bog deposits to the north of Amsterdam. In the village centre, a trench was cut through a terp (artificial mound) composed predominantly of clay sods, in order to obtain information on both the date of construction and on the intention of the builders. On the evidence of pottery fragments, the construction took place at the end of the thirteenth century AD. Samples for palaeoecologi-cal analysis were taken from the undisturbed peaty subsoil , the sods, and some dung layers. A wide spectrum of micro-and macrofossils was observed, including some newly recognized ones, which were described, illustrated and, if possible, interpreted. The spectrum of plant remains in the subsoil sample showed a pure raised bog environment with the characteristic strongly oligotraphic taxa. In addition to cultivation indicators, the medieval mixed soil surface just below the terp also provided evidence of temporary inundation with salt or brackish water. Apparently the former raised bog area was intermittently inundated soon after the reclamation, as a consequence of the drainage which caused oxidation and subsidence of the peat surface. The present study confirms other, partly unpublished evidence from archaeological sites indicating a much earlier increase of salinity (at least temporarily) of the encroaching Zuyder Zee than the generally accepted date of AD 1575.

Anthropogenic Indicators in Pollen Diagrams

Book

Full-text available

Jan 1986

Karl-Ernst Behre

Palaeocology and stratigraphy of the Lateglacial type section at Usselo (The Netherlands)

Article

Full-text available

Aug 1989
REV PALAEOBOT PALYNO

The present study is based on a detailed analysis of the Lateglacial type section from Usselo. In addition to pollen, seeds and insect assemblages many other hitherto unrecognized or incompletely known micro- and macrofossils are identified, described and figured and the palaeoecological significance is discussed.The new Usselo section spans most of the Lateglacial stratigraphical succession of the Netherlands. The base of the sampled section is dated c. 12,880 B.P. Since this sandy base already has thermophilous insects, it is evident that it begins after the initial climatic warming at the beginning of the Lateglacial.A considerable part of the Older Coversand II correlates with the relatively warm and treeless pre-Bølling s.s. period (= lower part of Bølling s.l.). During this interval macrophyte vegetation was very sparse. Coleoptera were rare and the most common beetles were species that live in damp sand where they feed on algae. Blue green algae of the Gloeotrichia-type apparently played a pioneer role thanks to their ability to fix nitrogen and thus make conditions in the shallow pool of Usselo suitable for other plants. At the start of the Bølling s.s. there was a great increase in the habitat diversity of both flora and fauna. Phytophagous Coleoptera show a much greater variety and there is evidence from the terrestrial beetles for a gradual reduction in the importance of the bare sand habitats.The more sandy layer which corresponds to the Earlier Dryas period does not show any marked change in either the local plant or insect communities. The sequence of aquatic macrophytes and helophytes equivalent to the older part of the Allerød period indicates that the pool was becoming progressively shallower and richer in nutrients. The continuous vegetational succession can be interpreted as due to the gradually improved nutritional status of the site leading to acidification towards the end of the Allerød. The succession of insect assemblages closely reflects that of the vegetation and the combined palaeobotanical and zoological data permit a very detailed reconstruction of successive local habitats.In contrast to the situation in western Britain where the insects suggest that the climate was warmer in Bølling time than in Allerød time, the insect sequence from Usselo suggests that the Allerød in the Netherlands was as warm as the Bølling (s.l.).Obligate cold climate insects were not found in the Earlier Dryas of Usselo. Evaluation of the existing 14C dates led to the conclusion that the most probable age limits of the Earlier Dryas in the Netherlands are 12,150±100 and 11,900±50 B.P.. This makes clear the approximate time-correlation with the cooling of climate in western Britain and the known standstill of the Scandinavian ice sheet. It is concluded that the strong environmental changes of the Earlier Dryas in the Netherlands (extensive dune-fields, frost-phenomena, death of birch trees resulting in renewed almost treeless landscapes) cannot be caused solely by climatic dryness, but that some temperature decrease must also have been involved.Temperature estimations for the Lateglacial, based on insects, plants and frost-phenomena are given and an attempt to reconcile all the evidence is finally made.

Physical evidence for the antiquity of Cannabis sativa L

Article

Full-text available

Jan 1998

1998. Physical evidence for the antiquity of Cannabis sativa L. (Cannabaceae). Journal of the International Hemp Association 5(2): 80-92. Cannabis has been an important economic crop plant for six millennia. Its uses for fiber, food, oil, medicine, and as a recreational/religious drug have been prevalent throughout this period. Recent palynological research into the agricultural and environmental history of Cannabis has produced curves for Cannabaceae pollen at a number of sites in Europe and America. Additional archaeological remains and written records provide evidence for both Old and New World occurrences. This paper discusses the origin, domestication and migration of hemp as a crop plant as documented by palynological and archaeological evidence. In addition, the comparative morphology of Cannabis and Humulus pollen grains is described, and the problems of interpreting Cannabaceae pollen in the stratigraphic record are discussed.

On the Medieval Climatic Anomaly

Article

Aug 2000

Stine

Problems in the interpretation of Cannabaceae pollen in the stratigraphic record

Article

Jan 1989

Annual lamination of sediments in Lake Lovojärvi, southern Finland, during the past 600 years

Article

Jan 1977

Le climat en Europe au Moyen Age: Contribution a l'histoire des variations climatiques de 1000 a 1425, d'apres les sources narratives de l'Europe occidentale

Article

Oct 1989

Dinàmica territorial de l'antiguitat a l'edatmitjana a Catalunya: arqueomorfología i estudi de casos

Article

Jan 1999

Josep Maria Palet Martínez

Über die spät- Und postglaziale Vegetationsgeschichte des Simmentals sowie die frühgeschichtliche und historische Wald- und Weiderodung auf Grund pollenanalytischer Untersuchungen

Article

Jan 1952

M. Welten

Untersuchungen zur Biologie und zur Ökologie limnischer Ostracoden aus der Umgebung von Hamburg

Article

Jan 1972

D. Hiller

The Ancient Cultivation of Hemp

Article

Mar 1967

H. Godwin

The discovery in a long pollen diagram from East Anglia of a substantial curve for a pollen-grain referable to Cannabis sativa , L., the Indian hemp, raised the hope that we might, through palynology, have the means of tracing the history of cultivation of this important and sinister economic plant in England and in Western Europe. It was clearly essential that pollen-analytic evidence should be related fully to existing historical and archaeological knowledge, and aided by a notice in this journal (ANTIQUITY, 1964, 287), and by the notable kindness of a great many academic colleagues, I have put together a condensed historical account of the plant in antiquity as preface to a description of the pollen-analytic data.

Lateglacial and early holocene paleohydrological and environmental change along a humid-arid transect from the central Pyrenees to the Ebro valley (Spain)

Article

Jan 2001

Palaeoenvironment of the valley of Ossau (Western French Pyrenees) during the last 27,000 years

Article

Jan 1988

A contribution to the knowledge of the cypridid ostracode fauna (Crustacea, Ostracoda, Cyprididae) on the Iberian peninsula, and a comparison with adjacent areas

Article

Jan 1992

Angel Baltanas

Limnología del Lago Grande de Estanya (Huesca)

Article

The history of the vegetation of Bory Tucholskie and the role of man in the light of palynological investigations

Article

Jan 1992

G. Miotk-Szpiganowicz

Describes the results of pollen analysis of the fossil lake sediments in three lakes in Bory Tucholskie (Lakes Maly Suszek, Suszek and Kesowo). 11 regional pollen assemblage zones are described which cover the period from about 11 810 yr BP to the present day. The 10 radiocarbon dates of organogenic sediment of Lake Maly Suszek and comparisons with the absolute age of certain events for Wielkie Gacno permit the use of a time scale. -from Author

Ostracods and palaeosalinity reconstruction

Article

Jan 1988

J.W. Neale

Ostracods are very sensitive to variations in salinity and have well defined salinity tolerances. A large amount of data in this field is available on Recent ostracods. This may be used by extrapolation back or analogy to determine the palaeosalinity of fossil sediments. -Author

Flora i vegetacio del Montsec (Pre-Pirineus Catalans). Institut d'Estudis Catalans

Article

Jan 1991

The Holocene: An Environmental History

Article

Mar 1991

The Cultural Landscape During 6000 Years in Southern Sweden--The Ystad Project.

Article

Jun 1993

Carbon and nitrogen determination of carbonate-containing solid

Article

May 1984

Two methods are described for determination of organic carbon, inorganic carbon, and total nitrogen in sediments, sediment trap materials, and plankton. Both methods discriminate organic and inorganic carbon by acidification, avoid losses of acid-soluble organic and inorganic matter, and utilize an automated CHN analyzer for all elemental determinations. Short-term precisions for organic carbon and total nitrogen are about +-1% of the measured value with blank levels less than 1.5 microgrammes for each element.-Author

Deforestation, Cannabis cultivation and Schwingmoor formation at Cors Llyn (Llyn Mire), Central Wales

Article

Mar 1986
NEW PHYTOL

S ummary Pollen and macrofossil diagrams from the schwingmoor sediments of Llyn Mire are presented. Prior to the formation of the schwingmoor, Cannabis sativa was cultivated around Llyn lake, first to the east and later to the west of the basin. Despite Cannabis cultivation so close to Llyn, there is no evidence to suggest that the lake was used for retting purposes. A period of woodland clearance occurred immediately after the Cannabis cultivation and this process may have been responsible for the changes which led to schwingmoor formation in the basin. It is suggested that increased soil erosion into the lake, together with some eutrophication, encouraged the colonization of the lake surface by a floating mat of vegetation. The schwingmoor was formed in historic times by a floating carpet of such taxa as Carex rostrata, Sphagnum recurvum and Sphagnum section Subsecunda. The mat was initiated in the western part of the basin. The use made of Cannabis/Humulus pollen density as a marker horizon in these studies demanded that these pollen taxa should be adequately separated, and the large numbers of grains of this type present in the sediments permitted the employment of numerical methods based on pore protrusion, which are described here.

New fossil evidence for the past cultivation and processing of hemp (Cannabis sativa L.) in Eastern England

Article

Nov 1981
NEW PHYTOL

S ummary Fossil records of Cannabiaceae pollen and Cannabis achenes from Flandrian deposits at three sites in eastern England are presented as further evidence for the past cultivation of this crop. It is suggested that retting of hemp to extract fibre was carried out at each of the sites.

La géochimie des éléments en traces dans la calcite des ostracodes: Principes, limites et perspectives de la méthode pour une reconstitution quantifiée des paléoenvironnements

Article

Dec 1999
Geobios

Guy Wansard

Ostracods are aquatic microcrustaceans with calcitic, bivalved carapaces. Recent studies high-lighted relationships between trace-element (mainly Sr and Mg) contents in ostracod valves and the temperature and chemistry of the host water. These relationships were successfully applied by several authors for quantification of paleoenvironmental reconstructions. This paper reviews the basics of the geochemical study of the ostracod shells and briefly describes new factors that play a role in the uptake of trace-elements and make the interpretation of the trace-element contents in fossil valves more complex. More geochemical studies through monitored laboratory cultures will provide better controls on ostracod shell chemistry and thus a better efficiency of the method for the quantification of paleoenvironmental and paleoclimate changes.

The Archaeological Significance of Patterns of Anomalous Vegetation on a Raised Mire in the Solway Estuary and the Processes Involved in their Formation

Article

Jan 2001

While the location and identification of archaeological features from vegetative responses on “dry-sites” is well understood in a British context, its application to wet sites is less well explored. Following the recovery of Glasson Moss, Cumbria, from a major fire in 1976, and a programme of hydrological restoration, a pattern of circular and linear features was observed during a field survey in the mid-1990s. Assessment of the archaeological significance of these features was undertaken in 1996 and 1997 using aerial photography, fieldwork and historical research. The results suggest that during the Early Mediaeval period, natural pools within the moss were used for hemp retting. It appears that water levels within the pools were controlled by the construction of narrow ditches with possible simple sluice systems. One pool was examined in detail; it was used for retting from c.7th century ad until it dried out during the late 12th to mid-13th centuries. Disruption to the mire hydrology, possibly combined with trampling activity around the pool and ditch, appears to have instigated vegetation succession, which resulted ultimately in the colonization of the edges of both pool and ditch by swathes ofCalluna vulgaris (heather). The time scale involved in these changes is unknown, although similar responses were noted as beginning to occur at the site of nearby tithe apportionment boundaries (narrow ditches) dating from 1816. This process of vegetation change is examined.

Stratigraphic Charcoal Analysis on Petrographic Thin Sections: Application to Fire History in Northwestern Minnesota

Article

Jul 1988

James S. Clark

Results of stratigraphic charcoal analysis from thin sections of varved lake sediments have been compared with fire scars on red pine trees in northwestern Minnesota to determine if charcoal data accurately reflect fire regimes. Pollen and opaque-spherule analyses were completed from a short core to confirm that laminations were annual over the last 350 yr. A good correspondence was found between fossil-charcoal and fire-scar data. Individual fires could be identified as specific peaks in the charcoal curves, and times of reduced fire frequency were reflected in the charcoal data. Charcoal was absent during the fire-suppression era from 1920 A.D. to the present. Distinct charcoal maxima from 1864 to 1920 occurred at times of fire within the lake catchment. Fire was less frequent during the 19th century, and charcoal was substantially less abundant. Fire was frequent from 1760 to 1815, and charcoal was abundant continuously. Fire scars and fossil charcoal indicate that fires did not occur during 1730–1750 and 1670–1700. Several fires occurred from 1640 to 1670 and 1700 to 1730. Charcoal counted from pollen preparations in the area generally do not show this changing fire regime. Simulated “sampling” of the thin-section data in a fashion comparable to pollen-slide methods suggests that sampling alone is not sufficient to account for differences between the two methods. Integrating annual charcoal values in this fashion still produced much higher resolution than the pollen-slide method, and the postfire suppression decline of charcoal characteristic of my method (but not of pollen slides) is still evident. Consideration of the differences in size of fragments counted by the two methods is necessary to explain charcoal representation in lake sediments.

Le chanvre ( Cannabis sativa L.) : une plante cultivée à la fin de l'âge du Fer en France du Sud-Ouest ?

Article

Dec 2002

Laurent Bouby

The ancient history of hemp (Cannabis sativa) is poorly documented in France and western Europe. Up to now, the oldest Cannabis seeds were not recorded in that area before Roman times. The waterlogged assemblage of the bottom valley site of Al Poux (Fontanes, Lot, France) delivered seeds that probably attest Cannabis cultivation in southwestern France as early as the Late Iron Age. Hemp was possibly grown in riverbank fields, but it could also have been carried to the settlement to be retted in the river. The special role of waterlogged assemblages in the preservation of hemp seeds is emphasised. It is stated that new investigations on this kind of context would be especially helpful to improve our knowledge of ancient hemp cultivation history. To cite this article: L. Bouby, C. R. Palevol 1 (2002) 89–95.

Variability in ostracod partition coefficients D(Sr) and D(Mg)

Article

Apr 1998
CHEM GEOL

Living and sub-recent ostracods were collected from four lakes and four springs, located in Belgium, France and Spain, characterized by low water Mg/Ca ratios (from 0.08 to 0.65). Valves of ostracods belonging to Cyprideis torosa, Candona neglecta, C. marchica and C. candida have been extensively analysed for their magnesium and strontium contents with respect to calcium. Comparisons of these results are made using the same elements from the waters in which the ostracod valves calcified. Our results offer new and somewhat different interpretations with respect to the uptake of Mg and Sr in the calcitic ostracod valves. These findings include the following. (1) The partition coefficient D(Sr) for ostracods belonging to the same genus (Candona) is not a constant. The observed variability in D(Sr) values could be due to the rate of biological calcification, although more investigations are necessary to assess the influence of this factor; it is possible that some taxa grouped under the genus Candona belong to a different genus. (2) Even at the species level (Cyprideis torosa), the ostracod D(Sr) cannot be considered to be constant. At low water Mg/Ca ratio (0.65), our D(Sr) value for C. torosa is higher than those determined by others for C. torosa calcified in evolved marine water. (3) The Mg/Ca ratio of the water appears as a major factor influencing D(Mg) for ostracods. For low water Mg/Ca values (

Pollen-analytic evidence for the cultivation of Cannabis in England

Article

Oct 1967
REV PALAEOBOT PALYNO

H. GODWIN

A detailed pollen diagram from an East Anglian Lake, Old Buckenham Mere, registers vegetational changes from Late Glacial time to the present. When a chronology is projected upon it this allows the reconstruction of the effects of historic and prehistoric man upon local vegetation through the last 5,000 years. Neolithic influence was slight, but in the Late Bronze Age and pre-Roman Iron Age there was progressive forest clearance associated with pasturage. In Anglo-Saxon time arable cultivation extended greatly upon heavier soils. Secale (rye) was cultivated from the Roman time and from Early Anglo-Saxon time there is a substantial continuous curve for a pollen grain recognisable as that of Cannabis sativa (hemp), upon microscopic criteria newly defined. It was locally cultivated in large amount in Late Saxon and Norman time when the region was heavily populated and in Tudor time cultivation of this crop was enforceable by law.

Paleosalinity from Trace Metals in Fossil Ostracodes Compared with Observational Records at Devils Lake, North Dakota, USA

Article

Mar 1991
PALAEOGEOGR PALAEOCL

The chemistry of closed-basin lakes responds directly to the hydrologic budget through evaporative concentration of dissolved salts, and the sediments of these basins contain several excellent fossil and geochemical proxies for past changes in water chemistry and salinity. The trace-metal content of ostracode shells, among the most promising of these paleosalinity methods, is further explored in this study of Mg and Sr partitioning in Candona rawsoni, a widespread ostracode of the North American Great Plains. The molar distribution coefficients KD[Mg] and KD[Sr] for this species, are determined from laboratory experiments in which C. rawsoni are cultured under controlled temperatures and salinities. Our formulation of KD[Mg] contains a correction term for excess Mg that is incorporated into the shell during early calcification.The accuracy of the distribution coefficients is tested against field collections of live ostracodes from a suite of 12 Dakota lakes. The KD-inferred values for (Mg2+/Ca2+)H2O and (Sr2+/Ca2+)H2O are in close accord with the same ratios measured in the lakes. A comparison of ostracode-reconstructed and historically measured salinities for Devils Lake, North Dakota, shows good agreement within the salinity range preferred by C. rawsoni (1–10%0), although salinity excursions beyond this optimum are poorly represented in the sedimentary record. In most lakes salinity is more readily inferred from (Mg/Ca)H2O than (Sr/Ca)H2O because Sr solubility is a complex function of several carbonate phases. As shown for Devils Lake, (Sr/Ca)H2O may not vary systematically with the salinity of some brines.

Greater drought intensity and frequency before AD 1200 in the Northern Great Plains, USA

Article

Dec 1996
NATURE

EXTREME large-scale droughts in North America, such as the 'Dust Bowl' of the 1930s, have been infrequent events within the documented history of the past few hundred years, yet this record may not be representative of long-term patterns of natural variation of drought intensity and frequency. In the Great Plains region of central North America, historical droughts have persisted longer than in any other part of the United States1, but no detailed records of drought patterns in this region have hitherto been obtained that extend beyond the past 500 years. Here we present a reconstruction of drought intensity and frequency over the past 2,300 years in the Northern Great Plains, based on lake salinity fluctuations inferred from fossil diatom assemblages. This record, of sub-decadal resolution, suggests that extreme droughts of greater intensity than that of the 1930s were more frequent before AD 1200. This high frequency of extreme droughts persisted for centuries, and was most pronounced during AD 200-370, AD 700-850 and AD 1000-1200. We suggest that before AD 1200, the atmospheric circulation anomalies that produce drought today were more frequent and persistent.

Extreme and Persistent Drought in California and Patagonia During Medieval Time

Article

Jun 1994
NATURE

Scott Stine

STUDIES from sites around the world1-5 have provided evidence for anomalous climate conditions persisting for several hundred years before about AD 1300. Early workers emphasized the temperature increase that marked this period in the British Isles, coining the terms 'Mediaeval Warm Epoch' and 'Little Climatic Optimum', but many sites seem to have experienced equally important hydrological changes. Here I present a study of relict tree stumps rooted in present-day lakes, marshes and streams, which suggests that California's Sierra Nevada experienced extremely severe drought conditions for more than two centuries before ad ~ 1112 and for more than 140 years before ad ~ 1350. During these periods, runoff from the Sierra was significantly lower than during any of the persistent droughts that have occurred in the region over the past 140 years. I also present similar evidence from Patagonia of drought conditions coinciding with at least the first of these dry periods in California. I suggest that the droughts may have been caused by reorientation of the mid-latitude storm tracks, owing to a general contraction of the circumpolar vortices and/or a change in the position of the vortex waves. If this reorientation was caused by mediaeval warming, future natural or anthropogenically induced warming may cause a recurrence of the extreme drought conditions.

Quantitative Interpretation of X-Ray Diffraction Patterns of Mixtures II. Adiabatic Principle of X-Ray Diffraction Analysis of Mixtures

Article

Dec 1974
J APPL CRYSTALLOGR

Flora Chung

All the information relating to the quantitative composition of a mixture is coded and stored in its X-ray diffraction pattern. It has been the goal of X-ray diffraction analysts since the discovery of X-rays to retrieve and decode this information directly from the X-ray diffraction pattern rather than resort to calibration curves or internal standards. This goal appears to be attained by the application of the `matrix-flushing theory' and the now-proposed `adiabatic principle' in applied X-ray diffraction analysis. The matrix-flushing theory offers a simple intensity-concentration equation free from matrix effects which degenerates to `auto-flushing' for binary systems. The adiabatic principle establishes that the intensity–concentration relationship between each and every pair of components in a multi component system is not perturbed by the presence or absence of other components. A key equation is derived which conducts the decoding process. Both the matrix-flushing theory and the adiabatic principle are experimentally verified.

Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz

Article

Oct 1998

A sediment core from a Mediterranean karstic lake was studied through its pollen, diatom, chydorid, ostracod, charcoal and authigenic mineral composition. Information about environmental history recorded in the sediment sequence since the Middle Ages is presented. The main fluctuations of water volume and trophic status of the lake occurred during periods of great change in land management and during climatic cold phases. The synergetic effect of these two factors led to a high water level phase and triggered a rising of the trophic level which produced meromixis. The onset of meromictic conditions at about 1700 AD coincides with the Maunder minimum in the Little Ice Age as well as with a period of increasing human population, woodland clearance and agricultural expansion to the detriment of the nomadic livestock breeding or transhumance (“Mesta”).

A palaeoecological study of an upper Late Glacial and Holocene sequence from “De Borchert”, The Netherlands

Article

Jan 1981
REV PALAEOBOT PALYNO

A section more than 3 m deep from “De Borchert” (near Denekamp, The Netherlands), which included part of the Younger Dryas and almost the whole of the Holocene, was studied by analysing the micro- and macrofossils per 0.8 cm in order to obtain maximum information regarding the regional and local vegetational succession and any climatic changes that might have taken place during that time interval.Newly recognised and recorded microfossils (fungi, algae, fossils of unknown taxonomic identity) are illustrated, described and interpreted. The analysis of pollen and other palynomorphs in combination with the analysis of macrofossils, permitted the following main conclusions:During the later part of the Younger Dryas the presence of certain herbaceous forms (e.g., Typha latifolia) indicates a minimum average July temperature of 12–13°C.A detailed reconstruction of the vegetational and climatic changes during the Preboreal could be made; the Friesland phase was a period of rising mean summer temperatures resulting in an expansion of Betula species (B. pubescens and B. nana). Drought was not yet a factor restricting the development of vegetation.During the Rammelbeek phase the increasing summer temperature caused a further increase in the rate of evaporation. Dry conditions prevailed which rendered the climate more continental. Regionally the decline of birches and an appreciable extension of grasses is characteristic of the Rammelbeek phase. The contemporaneous occurrence of thermophilous plants (Nymphaea alba, Ceratophyllum, and representatives of the Zygnemataceae) points to relatively warm summers (with mean July temperature of 13–15°C or even higher). The deeper depressions (e.g., the sampling site of the present section) did not dry out and during the Rammelbeek phase an acceleration of filling-in with vegetation (mainly Drepanocladus) could be observed.During the Late Preboreal the depression tracks apparently reached northwestern Europe. The summers became humid enough for the growth of Sphagnum. The amount of precipitation and the milder winters favoured the further spreading of trees.During the Atlantic period the small Sphagnum bog developed into a Betula carr.During the Subboreal the bog dried out causing a hiatus of ca. 1000 years (2450–3400 B.P.). From ca. 2450 to ca. 1000 B.P. the presence of prehistoric man in a settlement situated around the depression where the samples were taken strongly influenced the sample site. Fluctuations in population densities and economic changes are reflected in the pollen diagram. As a result of agrarian activities eutrophiation of the depression took place so that Alnus and Salix temporarily invaded the depression.

The cultural landscape during 6000 years in southern Sweden: The Ystad Project

Book

Jan 1991

Björn E. Berglund

Paleoecological studies in the Klokkeweel bog near Hoogkarspel (Prov. of Noord—Holland)

Article

Dec 1980
REV PALAEOBOT PALYNO

The course of filling-in and subsequent bog development of a brackish eutrophic lake is analyzed by means of investigations of pollen, spores, algae, fungal remains, diatoms and plant macrofossils. Some unknown and/or not generally known micro- and macro-fossils are described and illustrated. 14C datings and ignition residue determinations have been made.The analysis was expected to provide information about both regional and local vegetational developments, but the picture presented by the micro- and macrofossils is mainly local.In the lake sediment, deposited on a subsoil of marine clay, and the overlying peat the following phases in the vegetational succession have been defined: (a) initial phase with small elodeids, dominated by Myriophyllum spicatum; (b) littoral phase, characterized by vegetation types of Callitricho-Batrachion; (c) floating mat phase: Cicuto-Caricetum pseudocyperi, followed by a Caricetum paniculatae; (d) willow scrub with undergrowth of Dryopteris; and (e) birch carr.Salinity, alkalinity and trophic degree decrease with the advancing succession. The vegetation shows traces of human influence, but apparently the local succession is not strongly affected.The phase with birch carr shows two periods of wetter conditions, dated ca. 750 B.C. and ca. 600 B.C., respectively. The final period may explain the widespread abandonment of prehistoric settlements in West Friesland. The pollen diagram shows a mysterious maximum of Pinus from ca. 750 to ca. 650 B.C.

Cores of soft lake sediments

Article

Jun 2008
BOREAS

Herbert E. Wright

Short cores of soft sediment, used in studying the pollution history of lakes, can be obtained with a plastic tube fitted with a piston and piston wire. If the sediments of deep water are annually laminated (and thus difficult to sample without disturbance) or contain excess gas (which can disrupt the stratigraphy during its escape), a short ‘core’ can be acquired by producing a frozen crust on a tube filled with dry ice and butanol. A continuous core of soft lake sediment at least 7 m long can be obtained in a single drive beneath deep water with a hand-driven piston corer. Such a core assures the complete continuity necessary for counting annual laminations or for making close-interval analyses without fear of gaps, and it provides the uniform orientation required for measurements of paleomagnetic directions.

The Past Global Changes (PAGES) project: a personal perspective

Article

Mar 1999

Frank Oldfield

The present note seeks to provide a personal overview of the questions that dominate the research agenda of the PAGES project. These questions will be to the fore as PAGES research leaders develop a synthesis of the project and look ahead to the next stages in its development. An outline is presented of plans for considering, within the PAGES framework, the interplay of human activities and climate variability in the recent past.

2000-Year environmental history of a karstic lake in the Mediterranean Pre-Pyrenees: The Estanya lakes (Spain)

Abstract

No full-text available

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